Process and light-sensitive screen-sheets for the production of pigment images by transfer



May 28, 1963 w. M. BUSKES 3,091,529

PROCESS AND LIGHT-SENSITIVE SCREEN-SHEETS FOR THE PRODUCTION OF PIGMENT IMAGES BY TRANSFER Original Filed March 9, 1953 3 Sheets-Sheet 1 LOCATION OF LIGHT-SENSITIVE MATTER LIGHT-PERVI, SCREEN PART SCREE PART 6 UGHT-RERVIOUS SUPPORT OUS SUPPORT 6 ORIGINAL LIGHT-SENSITIVE SCREEN SHEET SITIVE MATTER REPRODUCIBLE IMAGE PORTION F; 9' 1 F: g- 5 Fig. .5

E25. 4 LIGI-ff-PERVIOUS SUPPORT I SCREEN PART UGTIT'PERWWS SUPPORT I A (-2 F ig-5: -1- ?l 2 LOCATION OF LIGHT-SENSITIVE 2 SCREEN PART MATTER LIGHT-SENSITIVE LAYER F25"- 5 Fag- .5

SCREEN PART 9 sPAcme OF SCREEN PART CENTERS I l sc PART V 71 r 4/71 r y/n s a 9 UGHT-PERVIOUS -T SCREEN Pon'noN LtGHT-PERVIOUS SCREEN PORTIONS NON-TRANSFERABLE SCREEN PARTs SCREEN PARTS TRANSFERABLE SCREEN PARTS 12 54 I5 SCREEN SHEET RECEM NG-SLPPORT INVENTOR. WILLEM MARIE BUiKES ATTORNEY May 28, 1963 w. M. BUSKES 3,091,529

PROCESS AND LIGHT-SENSITIVE SCREEN-SHEETS FOR THE PRODUCTION OF PIGMENT IMAGES BY TRANSFER Original Filed March 9, 1955 3 Sheets-Sheet 2 ex ose!) UGHT-SENSITIVE EXPOSED usrrr-ssua'nvs gen: SHEETAFTER mm. TRANS- 55m SHEET CARFMNG REMNANT UNTRANSFERRED SCREEN UNTRANSFERRED SCREEN |o as P T PART .o{ 4% 04 M p 1 K \T m\\\ 1 I NTRANSFERREDPORHONOF I2 mmss oscm: PART SFEPABLE scnssu PART mi i A LL I3 I I \\\n L L s u g a il-EQ Q2] I l :9 TRANSFERRED PART RECEIVING SUPPORT CARRYING OF SCREEN PART TRANSFER IMAGE RECEIVING SUPPORT CARRYING TRANSFER IMAGE Fr- 5 F7 10 Fgzll E LlGHT-PERVIOUS SUPPORT SCREEN PART N RECESS r l 1 l x 2 SCREEN PART IN RECESS 2o UGHT'SENSITNE MATTER E EMBOSSED SURFACE OF EMBOSSED SLRFACE OF SUPPORT SUPPORT LIGHT- PERVIOUS SUPPORT LIGH -SENSITIVE MATTER SURFACE L OF UGHT-SENSITNE LAYER lN RECESS LIGHT-SENSITIVE LAYER EMBOSSED SURFACE OF SUPPORT 2| 2O 11! T! J 2 UGHFPERVDUS SUPPORT LIGHT PERVIOUS SUPPORT INVENTOR. WILLEM MARIE BUSKES ATTORNEY May 28, 1963 5 ES 91,529

w. M. BU K 3 PROCESS AND LIGHT-SENSITIVE SCREEN-SHEETS FOR THE PRODUCTION OF PIGMENT IMAGES BY TRANSFER Original Filed March 9, 1953 3 Sheets-Sheet 3 SCREEN MOVABLE TO BLOCK EXPOSURE LIGHT SOURCE BLANKET FOR APPLYING MATERIALS TO EXPOSURE PAbEL ROLLER FOR APPLYING THIN LAYER OF TRANSFER LIQUID ID EXPOSED fiREEN I VIIIIIIIIIIIIIIIIII/ 6 4| PORT (SHEE RUBBER noun INVENTOR. wlLLr-m MARIE BusKES ATTOR N E! 3,091,529 Patented May 28, 1963 ice 3,091,529 PROCESS AND LIGHT-SENSITIVE SCREEN-SHEETS FOR THE PRODUCTION OF PIGMENT IMAGES BY TRANSFER Willem Marie Bushes, Venlo, Netherlands, assignor, by mesne assignments, to Chemische Fabrik L. van der Grinton N.V., Veulo, Netherlands, a limited-liability company of the Netherlands Continuation of application Ser. No. 341,197, Mar. 9, 1953. This application Aug. 19, 1958, Ser. No. 756,745 23 Claims. (Cl. 96-28) This invention relates to a process for the production of a pigment image on a receiving surface. In this process an image is first formed in a light-sensitive screen sheet, by image-wise exposure according to the procedure of screen refiectography. Its support is light-pervious and its screen together with the lightsensitive material is located at one side of this support. The screen which sometimes is referred to herein as a refiectographic light screen, consists of screen parts which are substantially impervious to the actinic light, alternating with lightpervious screen portions, without graded transitions between the impervious screen parts and the pervious portions.

This application is a continuation of my co-pending application, Serial No. 341,197, filed March 9, 1953, now abandoned.

In the process according to the invention, as it will be described, the image-wise exposed screen sheet cooperates with the receiving surface, whilst the light-impervious screen parts cooperate with the light-sensitive material, belonging to the sheet, in order to obtain image-transfer onto the receiving surface.

The invention also relates to light-sensitive screen sheets for carrying out the process and to processes for the manufacture of such light-sensitive screen sheets.

When in the following description reference is made to screen parts" then thereby are meant the (practically) light-impervious screen parts. Other screen portions are, in the following description, defined by means of other and supplemental wordings.

Since the processes and lightsensitive screen sheets according to the invention are concerned with screen refiectography, reference is made to French Patents 693,335 and 762,542, in the latter of which the application of various kinds of screens in cooperation with all usual lightsensitive layers is proposed. Up to now, screen reflectography has in practice only acquired significance when covering screens (screen structures with substantially iight impervious Screen parts) and positive diazoiayers (sec British Patent 425,126) are applied. Here the screen parts generally cover the surface to a considerable extent. In the process according to the invention such screen structures are used.

The use of a light-sensitive screen sheet, to wit a sheet with light-sensitive material and screen parts on one side of the support is already described in the above-mentioned British patent. Special light-sensitive screen sheets are described in Dutch Patents 62,005, 62,006 and 65,185 in which lasbmentioned two patents one side of the sheet has the form of a relief, in the cavities of which the screen parts may be located. In as much as the latter system will be applied in the process according to the invention and in the light-sensitive screen sheets for use in this process, the screen parts located in the cavities, are considered as being located at one side of the light-pervious support. As it is obvious from the literature referred to, working according to the procedure of screen reflectography implies that there be light-sensitive material lo cated between the screen and the original during the exposure, and that, taken in the direction of incident light the sequence always is: screen, light-sensitive material, original.

In the process according to the invention, the screen parts of the light-sensitive screen sheets have, in addition to their function of light-intercepting parts during the making of the reflex copy, also the function of a pigment matter which may be transferred image-lwise to a receiving surface. Selective transfer processes are known from US. Patent 1,118,479, US. Patent 1,618,505 (there called bodily transfer") and from British Patent 655,274. These transfer processes are isolated disclosures in the literature. On the one hand they are to be distinguished from the decalcomania and the transfer of photographic imagelayers, e.g. according to British Patents 510,233, 645,211 and 655,275, and the British Journal of Photography, 1928, pages 393-395, and on the other hand from selective-image-transfer by imbibition (diffusion) as described, for example, in British Patent 614,155. In the following description bodily or selective transfer are not separately referred to, butfor the sake of simplicityonly transfer." When not otherwise defined, the term transfer" implies transfer at room temperature.

In the process according to the invention, the screen parts of the light-sensitive screen sheet are accessible from the outside. If the screen parts are covered on that side which is turned away from the lightpervious support, for example with light-sensitive material, then they nevertheless are considered as accessible and the term accessible in this connection has, as will become clear from the following, a broader sense than that of directly touchable. They must visually contrast with the receiving surface.

According to the process of the invention, the receiving surface is, after image-wise exposure of the light-sensitive screen sheet according to the procedure of the screen reflectography, pressed against' the side of the exposed screen sheet which carries screen parts which are accessible from the outside and visually contrasting with the receiving surface and out of these screen parts the pigment image is formed upon the receiving surface, whereafter the two surfaces are separated.

The image formed by this image-transfer on the re ceiving surface is termed the transfer-image, the image remaining after complete transfer on the original screen sheet is termed the remnant-image"; this is the reverse negative of the transfer-image.

In order to make it possible to perform the transfer easily and reliably, preferably one or both of the surfaces is wetted. According to an excellent form of execution, whereby the possibility of the sheets cooperating in the transfer taking up needless moisture is avoided, moisture is applied in a thin layer of liquid, and the moistening in many cases, is combined in one operation with the pressing. An advantageous embodiment is that in which, by the transfer, all, or nearly all of the pigmentmatter of the screen parts present in the transferable image-portions, is transferred onto the receiving surface, so that when separating the original light-sensitive screen sheet and the receiving surface an image remains on both surfaces consisting of screen parts; one being the substratetive image of the other.

According to the process, a multicolor image can be made by forming different images in a number of screen sheets, each of which carries differently coloured screen parts and transferring in succession these images in superposition in register onto a receiving surface.

In a light-sensitive screen sheet for carrying out the above-mentioned process, the light-sensitive material is linked up with the screen parts, and the light-sensitive material is one which by the exposure produces a difference in transferability of at least parts of the screen parts, for the formation of the image on the receiving surface. In the light-sensitive screen sheets the linkage of the screen parts with the lightsensitive material naturally must be of such a nature, and light-sensitive material and screen parts must cooperate in such a way, that the difference in the light-sensitive material caused by the exposure actually can produce the difference in transferability. The transferability of the screen parts cooperating with light-sensitive material and the useful effect of the differences which come about upon the exposure, however apparently also is to a considerable extent a matter of adhesion (or adherence), either directly or by means of an intermediate substance, for example of light-sensitive material, to the light-pervious support, on the one side of which they are located. If this adhesion is too small, then it may occur that upon the transfer as carried out after the imagewise exposure, all screen parts will transfer, and then the transfer consequently is no longer selective; if it is too great, then under certain circumstances, after selective exposure, no transfer of screen parts onto a receiving support can be realized, and in consequence, as in the first case, no image will be formed. Thus the adherence to the light-pervious support has to be adjusted to the forces of adhesion between screen parts, light-sensitive material and receiving support, which become active upon the transfer-operation.

If in a light-sensitive screen sheet according to the invention, the above described factors are properly adjusted to each other, and if such a sheet is placed in contact with an original subjected to an exposure according to the procedure of screen reflectography, a screen reflex image will be formed in the light-sensitve material, which image, it is true, usually will have no visibility worth mentioning, and thus, without further treatment, will not be of use as an image, but which Will consist of image-portions having more easily (next to portions having more difficultly) transferable screen parts. Upon transfer, for example with the aid of water, onto a receiving support, for example paper (various other receiving supports will be described later), then in the more easily transferable areas, the screen parts (or parts thereof) will transfer onto the receiving support and will there form a pigment-image. The process according to the invention thus may advantageously be used for the making of copies from originals without continuous medium tones. From originals with continuous medium tones they will yield, it is true, copies, but in these the medium tones are imperfectly reproduced.

FIGURES 1-4 of the accompanying drawings illustrate some examples of the structure of light-sensitive screen sheets suited to the process according to the invention.

FIGURE serves to illustrate the screen structure.

FIGURES 6 and 7 illustrate two manners in which the screen parts and the light-pervious screen portions may be grouped in the screen pattern.

The FIGURES 8-10 illustrate the transfer-operation.

FIGURES 11-14 illustrate the structure of light-sensitive screen sheets, the screen parts of which are located in cavities as referred to in the following description.

FIGURE 15 illustrates the situation upon the imagewise exposure.

FIGURE 16 illustrates an apparatus for the pressing together of screen sheet and receiving support upon the transfer-operation, and FIGURE 17 illustrates a transfer-apparatus for combined Wetting and pressing together.

In the drawings, corresponding parts are always indicated by the same reference-numbers.

In FIGURE 1 (schematic cross-section) 1 is a screen part, 2 indicates the location of the light-sensitive material, 3 represents the light-pervious support, 4 the original with the dark image portion 5. The parts 1, 2 and 3 form one entity, to wit a light-sensitive screen sheet according to the invention. In the making of a screen reflex copy the light will impinge according to arrow 6.

In the structure of a screen sheet according to FIGURE 2 the screen parts 1 and the light-sensitive material 2 linked up with the screen parts 1, are located at the undersurface of the light-pervious support 3. Upon the making of a screen-reflex copy, the light, as in FIGURE 1, impinges according to arrow 6.

In the screen sheet according to FIGURE 3 the lightsensitive material 2 is located at both sides of the screen parts 1.

The screen sheet according to FIGURE 4 has a layer 2 containing light-sensitive material, so that this constitutes the light-sensitive layer.

FIGURE 5 schematically represents in cross-section the location of screen parts 1 next to light-pervious screen portions 8. The mutual centre distance (linear period) between the screen parts (and equally between the lightpervious screen portions mutually) is indicated by 9.

FIGURE 6 schematically represents a view of a screen pattern, in which the screen parts 1 have the form of islands and are encircled by the light-pervious portions 8.

FIGURE 7, like FIGURE 6, schematically represents a screen pattern in which, however, the light'pervious portions 8 have the form of islands and are encircled by screen parts 1.

FIGURE 8 is a schematic cross-section of the condition of a light-sensitive screen sheet 10, which, after imagewise exposure has been brought into adhering contact with the receiving support 11. The transfer zone is schematically indicated with a dotted line 2. For clearness sake in this figure, as in FIGURES 9 and 10, the light-sensitive material has not been shovm, but each time only the two supports (separate from each other) and the screen parts are indicated. It is supposed, that after image-wise exposure, the screen parts 12 and 13 are not transferable and the screen parts 14 and 15 are transferable.

FIGURES 9 and 10 illustrate the position after the transfer-operation; FIGURE 9 representing partial and FIGURE 10 complete selective transfer. In FIGURE 9 the exposed light-sensitive screen sheet is indicated at 10. From the screen part 14 (FIGURE 8) the part 16 (FIGURE 9) has been left over, but the part 17 has been transferred onto the receiving support 11. The same applies for screen part 15 (FIGURE 8) which in FIGURE 9 is split into 18 and 19. Even by this partial transfer a proper transfer-image may be obtained upon support 11, provided the parts 17 and 19 are sufficiently contrasting visually with the receiving surface of 11. The substratetive remnant-image on 10 however is poor. The nontransferable screen parts 12 and 13 have naturally remained on the original sheet.

In FIGURE 10 the result of complete selective transfer is represented in the same manner. On the screen sheet 10 the screen parts 12, and 13 were non-transferable after the image-wise exposure and have remained thereon. The transferable screen parts 14 and 15 have been transferred onto the receiving support 11. Proper images are now obtained on both supports. The remnant-image on 10 is the negative of the transfer-image on 11.

The light-sensitive sheet according to FIGURE 11 comprises a light-pervious support 3, in the undersurface of which by embossing, screen-wise distributed open cavities 20 have been made, by which, as it were, elevations 21 have been formed. In the cavities the light-impervious screen parts 1 are located. The light-sensitive material is again represented by 2.

In the schematic representation of FIGURE 12, the screen sheet according to the invention has a light-pervious support 3, in the upper surface of which screen-wise distributed open cavities 20, with screen parts 1 are located in between elevations 21. The light-sensitive material 2 is indicated by dotted line 2, which however now follows the profile of the support.

In the embodiment of a screen sheet according to the invention as illlustrated by FIGURE 13, the cavities 20 provided with screen parts I are located right in the lightsensitive layer 2.

According to the embodiment of FIGURE 14, 3 again is the light-pervious support. The screen-wise distributed cavities are situated in the upper-surface thereof between elevations 21. The screen parts 1, located in the cavities 20, are indicated, which however, are in this instance mixed with light-sensitive material.

FIGURE 15 schematically represents the cross-section of a printing apparatus, wherein 22 is a high-pressure mercury-vapour lamp for example of 42 centimetres length and a power of 700 watts, 23 an aluminium reflector and 24 a segment from a glass-cylinder with an outside-diameter of 19 centimetres. By means of a shade 25 revolvable around its axis along the path indicated by a dotted line, the surface to be exposed can be shaded from the light beams 26.

The screen sheet 10 to be exposed is, together with an original 29, with image-portion 27, pressed by means of the blanket 28 against the outside of the glass-cylinder, in order to achieve the required contact between screen sheet and original, and, with opened shade 25, irradiated from lamp 22 through cylinder 24.

FIGURE l6 schematically represents a simple apparatus, suitable for pressing together the screen sheet and receiving support. A rubber roller 30 is lodged in bearings 31 on the pedestal and is driven by means of crank 32. A rubber roller 33 is lodged on both sides in frame 34, which is supported on its sides (not shown). The springs 35 neutralize the weight of roller 33 and frame 34. On top of frame 34 a weight 36 is placed, which weight will determine the pressure of roller 33 upon roller 30. The rubber rollers have for example a length of 280 millimetres, a diameter of 40 millimetres and a hardness of 75 Shore.

FIGURE 17 represents schematically in cross-section a transfer-apparatus which combines the moistening and pressing-together to one operation. Roller rotates according to arrow 44 in the transfer liquid 47, which is stored in trough 48. Roller 45 is coupled (not shown) with the pressing-rollers 30 and 33, which rotate according to arrows 40 and 41. The pressing-rollers 3G and 33 have for example a diameter of 40 millimetres, a length of 280 millimetres and a hardness of 75 Shore. They exert upon each other a pressure, which can be adjusted to the requirements of a certain transfer operation carried out with a given screen sheet and receiving support.

Screen sheet 43-screened side downis conducted to pressing-rollers 30 and 33 via slot 42 over roller 45, which roller 45 moistens it at its screened side. The pressingrollers 30 and 33 press the moistened screen sheet 43 and the receiving support 46 together, which latterreceiving side upis being supplied via slot 37, whereafter the two sheets, in pressed together condition, leave the apparatus again in the direction of arrow 49'.

When in a given case it is desirable to moisten the receiving support instead of the screen sheet, the situation remains as indicated in FIGURE 17, with the ditference that 43 represents the receiving support (receiving side turned down) and 46 represents the screen sheet (screened side up).

The light-sensitive material, which is used in the lightsensitive sheets and in the processes according to the invention, is of the kind, which as a result of the photochemical reaction, undergoes an alteration, and brings about an alteration in the sheet. Said alteration takes place in those image-portions of the exposed sheet, which correspond with the light (white) image-portions of the original, and does not take place or only to a less extent in the non-exposed, or less exposed portions, which correspond to the dark portions of the original and the alteration, affects (as already mentioned and as will be explained more fully) the transferability of certain screen parts in the sheet, and can appear in form of an alteration of. the linkage of the screen parts to the light-pervious support or of their adhering power to the receiving support. By way of example the alteration in transferability may be based on an alteration in receptivity for water. In certain cases this property is alterated by the lightreaction in one sense, in other cases in the other sense. In other cases again the light-reaction is followed by a chemical after-treatment, after which the physical alteration then manifests itself. In most of the light-sensitive systems under consideration for the invention, the property chosen as an example, i.e. the receptivity for water, is reduced by exposure. With other light-sensitive systems, which however nevertheless belong to the same genus, the contrary is the case.

The light-sensitive material, used in the invention, is essentially of the same kind as that which already finds wide application in various photographic and photomechanical processes. This sort of light-sensitive material, as well as processes which can be carried out with it, are described in the literature in many variations.

For instance, reference is made to J. M. Eder: Ausfiihrliches Handbuch der Photographic," vol. IV, 2nd part, 1926, wherein on pages 73-77 the so-called pigment paper (carbon tissue) is described, as well as the making of pigment prints (carbon prints) therewith. sensitized pigment-paper (carbon tissue) also finds wide application in the intaglio-printing technique for the making of an image in a metal (mostly copper) surface. See Eder: l.c., 3rd part, 4th edition, page 110. Also known are light-sensitive pigment layers on light-pervious supports, see Eder: l.c., 2nd part, pages 2l22l5. The lightsensitive material in such sensitized pigment papers (car bon tissues) principally consists of bichromated gelatin.

Further in Eder: l.c., 2nd part, pages 245279, the gum'bichromate printing process is described. The lightsensitive material of sensitized gum-bichromate printing paper principally consists of gum arable and bichromate.

Light-sensitive material of the said kind is also used in producing relief printing matrixes. See: Eder: Rezepte, Tabellen und Arbeitsvorschriften, 16-17 edition, wherein on page 264 a process is described for producing relief printing matrixes in zinc. As light-sensitive material there is mentioned here a protein and bichromate. Furthermore there is described on page 275 a process for producing half-tone matrixes in copper; in which the light sensitive material is fish-glue, glucose (grapesugar) and bichromate.

The above-mentioned light-sensitive materials belong to the kind, in which, by photochemical reactions only, or by a photochemical reaction followed by an aftertreatment, an alteration (as compared to the situation before exposure) is effected, which involves a reduction of, for instance, the receptivity for water of the material.

Also suitable for use in the invention is light-sensitive material in which, by the photochemical reaction, a reversed alteration (as compared to the situation before exposure) is being effected. Such light-sensitive material mainly consists of a combination of a ferric-compound, tartaric acid and gum arabic as is used in the socalled pigment-dusting-on process as described in Eder: l.c., 4th part, 3rd edition, pages 27 and 28.

Another example of a light-sensitive material applicable to the invention is used in colour photography, see Eder: l.c., 2nd part, page 377.

Lyophilic binding agents (vehicles) which are used for compounding light-sensitive material of the said kind, are: the already referred to gelatin, gum arabic, proteins, and fish-glue, though also others are used, e.g. agar-agar, dextrin, casein, gum tragacanth, methyl cellulose, shellac, colophony, asphalt, synthetic resins and polyvinyl alcohol, see a.o. Eder: l.c., 2nd part, pages 2249, 379; 3rd part, pages 332 and 379; Kolloid-Zeitschrift, vol. 103, No. 2 (1943), page 167, and German Patent 684,425.

In addition to the chromates and ferric-compounds already mentioned, other substances have been suggested for composing light-sensitive material of the said kind. As examples there may be mentioned for example auramin, erythrosin, (tetraiodo-fluorescein), diazo-compounds, azido-styryl-ketones and azido-styryl-azides. For these, reference is made to Eder: l.c., 2nd part, page 39,

Dutch Patents 35,423 and 59,407; Kolloid-Zeitschrift, volume 103, number 2 (1943), page 167, and Fiat Report 813.

Also more complicated compositions of light-sensitive material, as described in German Patent 720,341 can find application in the invention.

As already indicated. and as in other processes in which matter is being transferred from one support onto another, water often plays an important part as a transfer-auxiliary in the process according to the invention. In the transfer-methods, which are most attractive for common practice, water is preferably used; this generally being even simpler than the use of heat.

In view of this light-sensitive sheets are particularly suitable for the process according to the invention whose light-pcrvious support is hydrophilic at the side, at which the screen parts are located (which is the case per so with natural tracing-paper and cellophanc"), or has been rendered hydrophilic at that side by the application of hydrophilic matter. This, in particular, otters advantages with respect to the release of the screen parts when these are hydrophobic. In case of transfer by means of water, hydrophobic screen parts per so have the advantage of better remaining intact during the transferoperation. This is particularly important when complete transfer is aimed at to obtain a proper remnant-image.

An embodiment of such a light-sensitive sheet, easy to realize in practice, is that, in which the side of the light-pervious support at which the screen parts are located, consists of :a completely or partially deacylated cellulose ester.

In general the transfer with the aid of a liquid is easier, if the screen parts of the light-sensitive sheet are porous.

There are various possibilities for assembly of the lightsensitive sheets for the process according to the invention. These are: that in which light-sensitive material is located between light-pervious support and screen parts (FIG- URE 1); that in which light-sensitive material is located at that side of the screen parts which is remote from the light-pervious support (FIGURE 2) and that in which light-sensitive material is located at both sides of the screen parts (FIGURE 3).

When carrying out the procedure of screen refiectography the first-mentioned sheet is positioned with its screen side turned away from the original (see FIGURE 1) the second lies reversed (see FIGURE 2) whereas the third sheet (according to FIGURE 3) may be used in both positions optionally.

A light-sensitive screen sheet according to FIGURE 1 is attractive because of its simplicity. The support must not cause, or cause only little, light-scatter; and it carries the light-sensitive material at one of its sides and over that material the screen parts.

The light-sensitive screen sheets according to FIGURE 2, the light-sensitive material of which is located on that side of the screen parts which is remote from the lightpervious support, are less simple in build. They however are found to have the advantages that they yield, in general, sharper reflex copies (provided the structure of the screen pattern be sufi'iciently fine) and that the necessary standard of transparency of the light-pervious support is less high. Morever, by means of sheets according to FIGURE 2 non-reversed images are obtained on the (generally non-translucent) receiving support whereas the remnant-image, when reprinted (for instance on blueprint paper to a non-reversed image, affords sharp reproduction.

As already pointed out there are in principle two methods of making a screen reflex copy by means of a lightsensitive sheet according to FIGURE 3. In one method the light-sensitive screen sheet lies with its screen side turned towards the original; in the other it lies in the reversed position. In the first method, the light-sensitive material, located between screen parts and support, is exposed all over, whilst the light-sensitive material, located at the other side of the screen parts, is exposed selectively in accordance with the original to be copied. In the second method the positions are reversed. When using these light-sensitive screen sheets attention must be paid to these circumstances. Thus, in a light-sensitive screen sheet that optionally must be used in one of both methods (i.e. in the first method too) the light-sensitive material between screen parts and support must be so selected that it will not, in consequence of its exposure, link the screen parts so strongly to the light-pervious support that these become non-transferable over the entire image-surface, this being of particular importance when complete transfor is the object.

The presence of light-sensitive material inside the screen parts will not cause inconvenience. As a rule, this light-sensitive material however will contribute but little to the formation of the image. Thus, for example, the screen parts of FIGURE 2 could be saturated with light-sensitive material, provided as schematically indicated by 2 in that figure, a suificient quantity of lightsensitive material be sufiiciently accessible to the light.

If lyophilic binding-agents are being used in the lightsensitive material of the screen sheets for the process according to the invention, then this material can be given the form of a layer. For the principle of FIGURE 2 this is illustrated in FIGURE 4. By this method, in general, the light-sensitivity of the light-sensitive screen sheets becomes greater than when this layer-form is not used. In the embodiments in which the light-sensitive material is used in layer form, the condition of the layer (more or less exposed) will, upon the transfer, determine the fate of the screen parts linked up with it. Naturally the linkage between light-sensitive material and screen parts must suffice. This requirement is easily realizable when using matter in layer form. In general, provided the layer meets the requirements, the layer form does not appear to hinder the sharp shearing of the more exposed image-portions from the less exposed image-portions.

Lyophilic binding-agents may be divided into those which will not dissolve in water at room-temperature and those which will dissolve at room-temperature. This distinction between non-dissolving and dissolving, of course, is not to be taken in the strict sense. Under the firstmentioned group of binding-agents one understands those, which when put in water (of room temperature) will at the most swell within a reasonable length of time, but will not distribute homgeneously throughout the water; an example thereof is gelatin. If a representative of the other group is put in water (of room-temperature) then within a very short time it Will homogeneously be mixed with the water; an example thereof is gum arabic. By using one or the other kind of binding-agents one then obtains according to the assembly of the light-sensitive screen sheet and according to the manner in which the light-sensitive material is used upon transfer by means of a liquid at room-temperature, different effects, each in themselves having their characteristic advantages.

This may be illustrated by the following:

For simplicitys sake each time a transfer process is being supposed, in which water at room-temperature, forms the transfer-auxiliary, whilst the use of a lightsensitive substance is being supposed, which, mixed with the lyophilic binding-agent used, decreases the receptivity for water of that binding-agent, or its solubility in water, upon exposure.

Thus, when working for instance in a screen sheet according to FIGURE 1 with a lyophilic binding-agent which will not dissolve in water at room-temperature, as, amongst others, gelatin, then, upon transfer, a remnantimage of good water-resistance is obtained.

When working with a layer of such a non-dissolving lyophilic binding-agent in a screen sheet according to FIGURE 4, the screen parts of the less exposed imageportions will be transferred, and the advantage is that the binding-agent according to the figure located underneath the screen parts will also transfer onto the receiving surface, which binding-agent then will bring about the attachment of the screen parts to the receiving surface, and this even, then the receiving surface, has no or little adhesive properties. By then giving the layer of the light-sensitive material, containing the binding-agent, an adequate thickness, one can transfer onto comparatively rough receiving surfaces.

When working with a screen sheet according to FIG- URE 1, having a lyophilic binding-agent when, like fish glue, is soluble in water at room-temperature, then in the less exposed image'portions this binding-agent will dissolve upon wetting and will, at least partially, be transferred together with the transferable screen parts onto the receiving surface. The transfer images thus obtained will be proof against finger marking, because on their surface which is exposed to this treatment they are covered with the binding-agent.

When working with a screen sheet according to FIG- URES 2 and 4, having a lyophilic binding-agent soluble in water at room-temperature, transfer with small quantities of liquid becomes possible. Upon treatment with a small quantity of liquid, the binding-agent will not yet dissolve in the unexposed portions, but will there become adhesive and bring about transfer of the screen parts linked up with it. The treatment with liquid will not be suflicient for achieving this same result in the exposed portions in which the solubility of the lightsensitive material has been decreased. Thus in these parts no transfer will take place and negative remnant-image will be the result.

It, with the structure of the screen sheet last described, the transfer is carried out with more liquid, then a positive remnant-image will be formed, from which remnantimage sharp copies, for instance on positive diazotype material can be made by contact-printing. In this course of things one may assume that by the greater liquidsupply, the binding-agent in the less exposed image-portions is being removed from the screen parts by dissolving, so that in these image-portions there is no, or little chance that the screen parts be attached to the receiving surface. In the more exposed portions the light-sensitive material has lost its solubility, but it still has a sutficient capacity for absorption of liquid to provide with the absorbed liquid an adhesive effect upon transfer, by which adhesive-efiect the screen parts of the exposed image portions may be transierred onto the receiving-surface.

When using a light-sensitive screen sheet according to FIGURE 4 one may with good result, use hydrophobic, non-porous or slightly porous, screen parts, in which case the support should preferably be hydrophilic. The transfer images thus obtained are more resistant against finger marking and damping, If the screen parts are strongly hydrophobic and non-porous or only slightly porous, then it is true, in consequence, the transfer is somewhat more diflicult, but one can, as will be indicated later, again promote the transfer by using high pressure and similar means.

The light-sensitive screen sheets according to FIGURE 4 in general have the further advantage of rendering readily possible the linkage between the light-sensitive layer and the light-previous screen portions. Thus such screen sheets offer good resistance to mechanical damage during manipulating, and this even where the linkage between screen parts and light-pervious support is weak, a feature which facilitates the transfer. These purposes are well realizable when both the light-sensitive layer and the portions of the light-pervious support with which it has direct contact, are hydrophilic.

Particularly sharp images are produced from screen sheets, the screen pattern of which is regularly shaped. This is true both for transfer-images as well as for remnant-images. A regularly shaped screen pattern especially shows to full advantage when the copying is done from originals of good quality, line-drawings and printed matter.

When using light-sensitive sheets according to FIG- URES 2 and 4 it is, as already indicated, important to pay attention to the fineness of the screen structure.

In sheets of this assembly a favourable mutual centre distance (centre-distance 9 in FIGURE 5) between the light-pervious screen portions, or, what amounts to the same, between the light-impervious screen parts (the linear period of the screen) lies bewteen and 20 microns. Provided the properties of the screen sheet are chosen to be sufiiciently favourable for transfer, screen sheets according to FIGURE 2 will, when having finer screen structures, yield better images with smaller quantities of light, under otherwise equal conditions.

The screen parts may have the form of islands (1 in FIGURE 6) but also the light-pervious screen portions may be islands (8 in FIGURE 7). The latter pattern is preferred, since the imperfections in manufacture of screen structure obviously have less grave consequences with regard to evenness of the image portions in the ultimate copies. When using this pattern the transfer may be carried out with greater reliability, this probably because the screen parts by their mutual coherence, will support each other in the act of transfer.

In the process according to the invention it is not neces sary (see FIGURE 9), that the screen parts are entirely transferable, i.e. are being transferred completely. When they however are being transferred completely (see FIG- URE 10), or at least are being transferred to a considerable extent, then in the original light-sensitive screen sheet a good (substratctive) remnant-image is formed suitable for reprinting e.g. by contact-printing by transmission.

Dependant on the colour of the screen parts, the nature of the light-sensitive material, the contingent aftertreatment, the transfer-method applied and the colour of the receiving surface, one obtains after transfer diiferent transfer-images and remnant-images.

Suppose, to give a practical example, that in a lightsensitive screen sheet one forms a screen-reliex-image from an original having dark letters (characters) on white paper; that the screen parts are black; that upon exposure the light-sensitive material which is linked up with these screen parts, in so far as it is situated above the white areas of the original, undergo (like for example chromatc-gelatin) an alteration, by which its adhesive properties decrease; that the receiving-support consists of white paper, and that the transfer takes place with the help of a thin layer of water at room-temperature, then after separating both supports one obtains on the receiving support a black-on-white positive-i.e. a positive transfer-image-and if the transfer is sufiiciently complete, one has left a transparent negative image of the original-lo. a negative remnantirnageon the exposed original screen sheet.

Suppose the copying were done from the same original, and that the screen parts were white and the receivingsupport black, then the transfer-image would be negative. It must be pointed out here, that with exclusively white pigment it is only possible to obtain a light-imperviousness, as required for screcn reflectography, by giving the screen parts considerable thickness.

Suppose, one selects a light scnsitive material, the adhesive properties of which are increased by exposure, then with black screen parts and a white receiving support one obtains a negative transfer-image and a positive remnant-image from the original.

The screen parts may be formed from various materials. The substances used therein for bringing about the light imperviousness can best be summarized under the known term of pigment. Soot, graphite, ochre. and also white-lead, baryta and titanium dioxide are the most usual for obtaining a good covering power. In the screen parts, they are generally used in admixture to one or more 11 substances such as asphalt, gelatin, gum, polymers, cellulose, cellulose-derivatives, proteins, caseins, oils, etc.

As light-sensitive material for the screen sheets according to the invention, one can, as already pointed out, select a material which requires a chemical after-treatment for bringing about the alteration in the properties which are important for the transfer. An example of such a material is a diazo-colloid layer, as described in Dutch Patent 25,053, which, after exposure undergoes a treatment with chromate. According to the invention such an after-treatment can be combined with the transfer-operation, if a liquid is being used therein, by dissolving the chemical for the after-treatment in said liquid.

From the point of view of cleanliness and simplicity however, processes are being preferred using light-sensitive screen sheets, the light-sensitive material of which is one, which by exposure only (without chemical aftertreatment) will be altered in such a way, that it can bring about a difference in transferability of the screen parts linked up with it, as compared to that transferability in the condition before exposure.

It will be clear, that the light-sensitive screen sheet can be adapted to the transfer-method by which the images are to be formed. Screen sheets, the light-sensitive material of which upon exposure, or upon exposure plus aftertreatment, alters its adhesive power (adhesive power also implies adhesive power in wetted condition) naturally are particularly suitable for the processes according to the invention. The transfer is carried out with or without a transfer liquid, or with or without the application of a temperature higher than the ambient temperature. In combination with a screen sheet according to FIGURE 1, there is preferably used a receiving support, having an adhesive surface (at least adhesive during transfer), which surface will under pressure take over those screen parts from the reflex copy on the screen sheet underneath which the adhesive power of the light-sensitive material is small or has been made small by the exposure. Also an adhesive can be added to the transfer liquid. If in the cases represented by the FIGURES 2v and 4 contact with a receiving support is achieved under pressure, those screen parts which are in contact with the areas of the light-sensitive layer which have the greatest adhesive power will be transferred onto the receiving support. Also in these cases the receiving support may itself have some adhesive properties, but in these cases this in general is not of importance.

When transferring by the aid of water those lightsensitive screen sheets are of particular interest in which the light-sensitive material upon exposure, or exposure plus aftertreatment, alters its receptivity for water. In this respect particularly the assembly according to FIG- URES 2 and 4 comes to the fore as being important.

Light-sensitive screen sheets, the light-sensitive material of which is one whose power to swell with water alters by exposure or exposure plus aftertrcatment, find similar application. These are of equal importance in an assembly according to FIGURE 1 as in an assembly according to FIGURES 2 and 4. When using these screen sheets, methods of transfer are used in which water as well as heat and pressure may play a part. They are particularly advantageous when transferring onto rough surfaces. In general they require less pressure for being transferred.

Power of swelling with water naturally implies receptivity for water. On the other hand however receptivity for water is sometimes found in cases in which the swelling power is only small. In general it is impracticable to discriminate sharply between receptivity for water, adhesive power upon wetting and swelling power. In practice one naturally will have to take into account that the ambient atmosphere will always contain water vapour, so that Water indeed always will influence the transfer.

In all the embodiments described, those light-sensitive screen sheets, the screen parts of which are transferable as long as the sheet is in the unexposed condition and the light-sensitive material of which upon exposure alters to the extent that it will decrease the transferability of the screen parts linked up with it, in general give the best results. This sort of light-sensitive material offers, as has already been shown by the cited literature, the widest variety and it can be adapted to many different transfer methods.

It however must be pointed out that it may occur that a screen reflex oopy produced in a given light-sensitive sheet, which upon the application of a given transfer method will on a given receiving support yield a given transfer image (e.g. a positive), will, when the transfer method is altered, yield no or even a reversed (negative) transfer image on the same receiving support. In the foregoing a case has already been described in which moistening with little liquid gave a result different from the one which was obtained by moistening with more liquid. In the examples a case will be described, in which, under otherwise entirely equal circumstances, purely by selecting a different transfer temperature, such a reversal of result will be achieved.

Amongst the light-sensitive systems, which, upon exposure, alter to the extent, that they will decrease the transferability of the screen parts linked up with them, there are found systems which worlt without any bindingagent. Some light-sensitive compounds, like, e.g., certain condensation products of diazo compounds with formaldehyde are capable of yielding light-decomposition products, which probably are capable of polymerising. These may influence the transferabiiity if screen parts being linked up with them. Systems, containing a lyophilic binding-agent however are preferred.

In the first place the classical combination of chromate and colloid should be considered. Such light-sensitive .material in general has a low stability but at low temperature it nevertheless may be stored for a reasonable length of time. Chromate colloid systems of greater stability are known from US. Patent 2,526,759. A chromatc colloid system may be considered as a mixture, consisting of two substances which each per so are insensitive to light. The mixture, however, will react upon exposure. In other cases one has to do with a colloid plus a substance, such as a diazo compound, which without admixture of a colloid will undergo an alteration upon exposure. Upon exposure these substances will yield light-decomposition products which, with or without an aftertreatment or with or without a colloid, will bring about the alteration necessary for the invention (compare Netherlands Patent 25,053, already cited and particularly the aftertreatrnent described in this patent). Diazolayers in general are of better stability than chrornate layers.

Particularly suitable for the invention are the diazo compounds according to Netherlands Patents 35,423 and 35,480, the light-decomposition products of which have the property of precipitating proteins, and which are used in combination with lyophilic binding-agents. Reflex-copies on screen sheets made up with such light-sensitive material require no chemical aftertrcatment for becoming adapted to transfer, provided one does not include the use of a liquid, generally water (to which one cannot, at any rate not explicitly, attribute chemical action) in such transfer as a chemical aftertreatment. Particularly adapted for use in light-sensitive screen sheets according to the invention obviously were the condensation products of diazo compounds with a compound containing a reactive carbonyl group. Also these, upon exposure, will produce light-decomposition products, having the property of precipitating proteins.

Also aromatic azido compounds, as described in Netherlands Patent 59,407, are suitable for use as lightsensitive material in the invention. Azidostyryl compounds have been found to possess good activity.

Screen sheets which are of particularly good quality with respect to their evenness of screen structure and which moreover have the advantage that they can be manufactured by a relatively simple process, have the screen parts located in a screen form system of cavities (compare FIGURES 11, l2, l3 and 14). These lightsensitive screen sheets then have a structure similar to that of the light-sensitive screen sheets, described in the Netherlands Patents 62,006 and 65,185. However, among other difference, they are distinct from these by their light-sensitive material and thus by their utility for the process according to the invention. Also their assembly system is sometimes different (compare FIGURES 11 and 14). The peculiar linkage the screen parts have with the cavities on one hand produces a relatively good resistance against damage upon manipulation, whilst on the other hand the transferability, and therewith the ease of transfer are greater than is the case with screen sheets in which the screen parts are not located in cavities. Probably this can be explained by the lateral pressure exerted on the screen parts during the transfer operation, which lateral pressure cannot make the screen parts located in the cavities shift sidewards and can thereby contribute to the loosening of the screen parts from the support. More in particular this seems a plausible explanation in the case of funnel form cavities. In a light-sensitive screen sheet according to FIGURE 12 the screen parts are located in a screen form system of cavities in the light-sensitive layer. Naturally it is not essential that the light-sensitive material strictly follows the relief of the support as is the case in FIGURE 12. The support may be fiat and the relief is than exclusively formed in the light-sensitive layer as is the case in FIGURE 13.

The screen sheets of FIGURES l2 and 13 essentially function like those according to FIGURE 1 and in principle they have the same advantages. However, they have the further advantage that they are more resistant to damage on manipulation than the screen sheets according to FIGURE 1, the screen parts of the latter being more exposed. Of particular value is the light-sensitive screen sheet of the structure of FIGURE ll, in which the sheet is built up in sequence as follows: a lightpervious support with at one side a screen form system of originally open cavities in which are located the screen parts and thereover a layer of lightsensitive material containing a lyophilic binding-agent, which layer screens off the system of originally open cavities containing screen parts. In particular these screen sheets show the advantages of the enclosed location of the screen parts. Preferably the layer of light-sensitive material is in this case linked up with the light-pervious screen portions, formed by the elevations of the light-pervious support. Advantageously in this structure the screen parts are given only a small degree of adherence to the lightpervious support. This facilitates the transfer. When the cavities have funnel form, as shown in FIGURE ll, then this assembly has the further advantage of great light-efficiency combined with the advantage (in the screen reflectographic process) of a relatively large lightsensitive usefully active surface (i.e. that part of layer 2, which is located under the screen parts 1). The lightsensitive screen sheets described above can be manuf actured in numerous ways. In the following some preferred processes for this are described:

A relatively simple method for producing screen sheets according to FIGURE 1 is the following; one starts with a film, which causes little or no light scatter. It carries the light-sensitive material at one side. The light-sensb tive side of the film takes the screen parts over from a screen matrix in which matrix these parts are located, the screen parts adhering thereto. The linkage between the screen parts and the support (via the light-sensitive ma terial), as it ultimately will have to exist, can be made greater and smaller at will, and this circumstance is used to bring about such linkage between screen parts and support as required for separating the screen parts again from the support upon transfer. Where the light-sensitive material is capable of providing the desired adhesive power (if necessary after having been moistened) then this adhesive power may be used for taking over the preformed screen parts. By preformed screen parts" there should be understood screen parts which will not flow; they must be capable of being taken over from the screen matrix, preferably in their entirety, so that they must loosen from the screen matrix. This depends to a considerable extent on the nature of the surface of the screen matrix in which they are located, but also on the composition of the preformed screen parts themselves. The adhesive power of the screen parts towards the matrix must be smaller, preferably considerably smaller, than the adhesive force with which they are taken over. A number of suitable matrixes and compositions for screen parts will be described in the examples.

The following is another simple method for the manufacture of light-sensitive screen sheets according to FIG- URE l: The screen parts are formed in a screen matrix as indicated above. The layer of light-sensitive material is applied on the screen matrix thus filled. Thereafter this light-sensitive material, together with the screen parts present in the matrix are transferred by means of adhesion from the screen matrix onto the film, causing little or no light scatter. Again, as above indicated, the linkage between screen parts and support must finally be so balanced that the screen parts, at least partially, can again be separated from the support. Also in this method the layer of light-sensitive material can, e.g. after having been moistened, supply the necessary adhesive force.

In the above process for producing light-sensitive screen sheets the light-pervious sheet preferably contains a cellulose ester, the surface or surfaces of which have been more or less deacylated.

In another simple process for the manufacture of lightsensitive sheets, according to the invention, one side of the light-pervious support, preferably a film causing little or no light scatter, is made to take over, by adhesion, from a screen matrix, screen parts mixed with light-sensitive material, said parts being located in preformed condition in said screen matrix. Naturally the linkage between support and screen parts again must be so moderate that upon transfer they can at least partially be separated again. A suitable composition for forming the screen parts can, for example, consist of a combination of a lightsensitive substance with a lyophilic binding-agent to which be added the pigment, which will give the screen parts sufficient imperviousness to light. Such a mixture may, in a certain sense, be compared with the light-sensitive material as in general use in pigment paper (carbon tissue).

However there are distinct advantages, particularly with respect to light-sensitiveness, in keeping the screen parts and the light-sensitive material separate. Light-sensitive screen sheets of this kind can be manufactured by attaching to one side of a light-pervious support, e.g. a film, screen parts from a matrix, in which they were located in preformed condition. In this manner, there is formed 'on the light-pervious support a screen without graded transitions between the light-pervious screen portions and the screen parts. The screen parts are accessible from the side remote from the light-pervious support. The screen side of the so-formed screen sheet is provided with light-sensitive material which upon exposure undergoes an alteration, bringing about a difference in transferability of the screen parts, as compared to the transferability of these parts before exposure. The operations of transferring the screen parts from the matrix to the support and that of applying the light-sensitive material are so carried out that, in the finished screen sheet, the linkage of the screen parts with the light-pervious support will be so balanced that the screen parts can, at least partially, be separated again from the support.

When in the manufacture of this kind of lightscnsitive screen sheet there is used a light-sensitive material which contains a lyophilic binding-agent, it is applied to the accessible side of the screen parts in the form of a layer. Substances, such as gelatin, gum arabic, polyvinyl-compounds etc. will easily bring about the required linkage with the screen parts. Such a layer of light-sensitive material containing a lyophilic binding-agent may, for example, be applied onto the screen parts by a casting process.

The thickness of the layer of light-sensitive material which in this process is applied to the accessible side of the light-impervious screen parts, will naturally have great influence upon the properties of the light-sensitive sheet.

A light-sensitive screen sheet, particularly adapted for transfer by means of water, is obtained. in the above described process, if the side of the light-pervious support, with which the screen parts have been linked up is hydrophilic. Thus a sheet with good properties for transfer with water will be obtained if, in the above process a cello phane film or a sheet of natural tracing paper is used as the light-pervious support. Also one can make the side of the support which has to be screened hydrophilic by the application thereto of a separate layer. Good screen sheets are obtained if one starts from a light-pervious support containing a cellulose ester, which is completely or partially dcacylated at the surface with which the screen parts have to be linked. Where the side of the support which has to be screened is hydrophilic, a hydrophobic substance is preferably chosen for the screen parts.

A method for the manufacture of screen sheets, which is easy to carry out and which has its screen parts located in cavities is the following:

One side of a film, causing little or no light scatter, is provided with a light-sensitive material containing a lyophilic binding-agent, and in the layer of light-sensitive material there is formed, as represented in FIGURE 13, a screen form system of open cavities. Generally the layer of light-sensitive material will be temporarily softened, e.g. by moistening and/or heating, and the screen relief then impressed therein. The screen parts are thus formed in the cavities of the screen relief. The impressing of the relief naturally must be so carried out that in the final product sufficient quantities of lightsensitive material will still be located between screen parts and support.

Another process is carried out as follows (compare FIGURE 12): In a film, causing little or no light scatter a screen form system of open cavities is impressed in one side and said side is provided by application and/or by impregnation, with light-sensitive material. This is so carried out, that the outer side of the light-sensitive material substantially shows the same relief as that with which the process was started. The screen parts are formed in the cavities. This process, preferred to the foregoing, ensures the presence of an adequate quantity of light-sensitive material underneath all the screen parts.

A good variant of the last described process uses a film causing little or no light scatter, with, at the least at one side, a cellulose ester layer showing a screen form system of open cavities. This side of the support is subjected to a deacylating operation and thereafter is impregnated with a substance, which, together with the deacylated constituents of the support, forms a lightsensitive material which upon exposure will so alter that it can bring about a difference in transferability of the screen parts, linked up therewith, as compared to the transferability previous to exposure. Thereafter the system of cavities is filled with a substance from which hydrophobic screen parts are formed. In these lightscnsitive screen sheets the linkage of the screen parts to the support and their transferability upon moistening is determined by the light-sensitive material underlaying the screen parts.

Screen sheets according to FIGURE 14 are manufac- 16 tured by a simple process, consisting of filling the screen form system of cavities in one side of a light-pervious support, preferably a film, causing little or no light scatter with a substance from which screen parts mixed with light-sensitive material are formed.

A better process is the one in which the system of screen cavities is filled with screen substance, not mixed with light-sensitive material, whereafter the screen parts formed, are coated with light-sensitive material at their accessible side. This process will yield light-sensitive screen sheets according to FIGURE 11.

Preferably this process is again so carried out that a light-sensitive material containing a lyophilie bindingagent is applied in the form of a layer, e.g. by casting this material on the accessible side of the screen parts. This layer will at the same time make contact with the elevations 21 of the light-pervious support 3, which are free from screen substance.

If the relief side of the light-pervious support is hydrophilic, then in this process good linkage between the light-sensitive layer, which practically will always contain hydrophilic light-sensitive material, and those parts of the light-pervious support which form the light-pervious screen portions, which appear in the system as elevations 21 of support 3, can very well be achieved, this good linkage being desirable in these light-sensitive sheets.

A preferred process, which, on one hand can perhaps not be called extremely simple, but which, on the other hand will yield particularly suitable light-sensitive screen sheets of great evenness according to FIGURE 11, is the following:

A light-pervious support having at least at one side a cellulose ester, with at that side a screen form system of open cavities is used. This support is subjected, at least at its relief side, to a deacylating operation. Thereafter the cavities are filled with hydrophobic screen parts. Now there is deposited the light-sensitive material at that side of the screen parts, which is remote from the light-pervious support. Again, preferably, the layerform is used in this case. Light-sensitive screen sheets are obtained which are easy to manipulate without damage, even if the linkage between the hydrophobic screen parts and the deacylated surface of the cavities 20 be kept low. It is likely that the stability of these screen sheets is due to the fact that the layer of light-sensitive material is solidly linked up with the elevations 21 of the support, which are free from screen substance and consist of dcacylated cellulose ester. The pressing together necessary for transfer will preferably be carried out so that the two cooperating sheets (screen sheet and receiving support) are laid upon each other with the liquid between them and then passed through pressing rollers. In this manner the occurrence of airbubbles and similar difficulties which may occur in other compressing methods is avoided. Where the application of a thin film of liquid to the screen side of the screen sheet is suilicicnt to bring about good image transfer upon pressing, then a simple apparatus, as described in Netherlands Patent No. 53,196, can serve this purpose. This apparatus will apply, at a speed of 13 m./min., quantities of liquid of the order of magnitude of 8-10 g./m. naturally this quantity will vary with the receptivity for liquid of the surface.

if the receiving support is suitable therefor, then the thin film of liquid can also be applied to it. If desirable for good transfer one may apply a thin layer of liquid to the screen side of the screen sheet as well as to the receiving support. In many instances the apparatus for the application of the liquid and the apparatus for compressing the two sheets may be combined to one apparatus. The pressing together may, as a matter of fact, normally be carried out directly after the application of the liquid. If screen sheets of an assembly as illustrated in FIGURE 4 contain gelatin in their lightsensitive material they will as a rule require a larger 17 quantity of liquid per m?. In this case the quantity of liquid applied can be increased by using more than one thin film apparatus according to Netherlands patent No. 53,196.

in general it is advantageous to moisten the original light-sensitive sheet and not the surface of the receiving support upon which the image is being transferred. This indeed in some cases is not readily possible, e.g. when the receiving support has a hydrophobic surface, or has a metal surface, a glass surface and the like. If however the receiving support is suitable therefor, then it may under certain circumstances offer advantages to moisten also (or only) its surface.

The separation of the screen sheet from the receiving support can as a mile be carried out shortly after they have been pressed together. This will moreover increase production speed. Postponement of separation is sometimes disadvantageous for the quality of the transfer images and the remnant images. Naturally the final transfer images and the remnant images should be dry. If the transfer is carried out with a thin layer of liquid then the images will dry out after a reasonably short time.

Although in general the transfer is carried out at room temperature, in some cases application of heat in the transfer may be useful. Preferably this heat will be applied to the rollers by means of which the transfersurfaces are being pressed together. Under certain circumstances this will yield better transfer and will at the same time have the advantage that part of the liquid, if any is applied, will be eliminated by evaporation.

it has already been remarked, that the transfer is in some cases incomplete. If a screen sheet has an assembly according to FIGURES 2, 4 or 11 and if the screen parts have insufficient cohesion, then upon transfer they only will partially pass over to the receiving support. The remnant-image, then formed, will be imperfect, but the transfer image, provided there has been transferred a sufficient quantity of pigment, can still be excellent. This feature may be used to advantage, provided the quantity of pigment available in the screen parts is large, by using the imperfect remnant-image, formed upon the first transfer, for a second and even for subsequent transfers, each time naturally upon another receiving support. From one and the same image-wise exposed light-sensitive screen sheet a number of transfer images can thus be obtained until exhaustion of the transferable pigment in the remnant image is reached. During this repeated transfer the quality of the remnant image improves each time and upon the exhaustion of the transferable pigment a perfect remnant image will ultimately be obtained.

With an assembly of the screen sheet as in FIGURES 3 and 14 similar cases may occur.

If the light-sensitive screen sheet, the screen parts of which have incomplete coherence, is assembled according to FIGURES 1, l2 and 13, then upon transfer different results may be obtained. With this assembly an imperfect, in most cases even useless, transfer image, could be formed upon the first transfer, even if nevertheless a good remnant image would be formed, with which remnant image still further transfers could be carried out provided the pigment available in the screen parts be sufficient for repeated transfer. This repeated transfer, however, naturally can as a matter of principle always be carried out with remnant images and with transfer images if sutficient pigment is available in the screen parts and if the internal coherence in the screen parts is incomplete. Visual pigment images obtained by transfer can, as already pointed out, be made on various receiving supports. In the first place. naturally, papers should be considered. Their suitability depends on various factors, as for instance the structure of their surface, its hardness, the pH at the surface and the like. Inasmuch as water is used in the vast majority of cases as an auxiliary in the transfer, it can be said that in general papers upon the surface of which one can write with an aqueous ink come into consideration. Normal smooth writing paper, paper for typcwriting, printing paper and similar papers are adequate receiving supports. Particularly suitable are papers, which by their nature have a closed smooth surface or papers the surface of which has been smoothed and closed by an aftertreatment as, for example, the so-called glossy coated papers and similar papers (hereinafter for brevitys sake referred to as coated papers).

Papers having a rough surface will preferably be used as receiving supports together with light-sensitive screen sheets according to FIGURE 4 or FIGURE 11, which have a light-sensitive layer, which in the transferable areas has reasonably great swelling power with the trans fer liquid employed. Water being the natural auxiliary, the swelling power with water will be the property here mainly under consideration.

Apart from the qualities of paper already mentioned transparent papers may be used as receiving support. According to the invention transfer images thus formed, serve for the production of further copies by contactprinting (with light-transmission) cg. on diazotype papers. This is also true if transparent films and similar sheets are used as receiving support. The transfer can also be carried out with good success upon a metal surface, e.g. upon an adequate metal plate. Beautiful results also are obtained when the transfer is carried out upon glass, milk glass, artificial resin pro-ducts and the like. For obtaining decorative effects the transfer can be carried out upon a suitable ceramic surface, eg on the surface of a ceramic product which is still being processed and which thereafter will have to be finished by burning in, glazing and the like. The composition of the screen parts is then adapted to the desired object and the pigment in the screen parts is so chosen that the final effect to be achieved on the ceramic surface will come about during its further processing.

When the receiving support is not transparent, it can be advantageous to form a transfer image on both its sides. This naturally can be done simultaneously, e.g. by positioning a sheet-form receiving support, if necessary together with auxiliary liquid layers, between two exposed screen sheets. The sandwich is thus pressed together and thereafter the three sheets are again separated from each other. This double-sided method can, for example, be applied when copying originals printed on both sides, such as pages from a book or periodical.

In the foregoing a number of screen sheets has already been described, which for the transfer require an auxiliary adhesive. In other screen sheets such an auxiliary adhesive is not properly necessary, but in many cases it will nevertheless be of help, e.g. for an improved linkage (anchorage) of the screen parts in the transfer images. A process to this end provides that the liquid used in the transfer contains an adequate adhesive. Another process, which with certain screen sheets will give good results is that in which the transfer is carried out on a receiving support, the receiving surface of which is so processed that it will, at any rate during the transfer process, dis play adhesive properties. Generally this again is done with simultaneous application of a transfer liquid.

It has already been pointed out that the transfer is due to a balancing of adhesive forces. This must be taken into account when adhesives are used in the transfer liquid or on the receiving support, for, as pointed out already in the foregoing, a too great adhesion towards the receiving support may result in transferring from the image-exposed screen sheet not only the screen parts of greater transfer-ability but also the screen parts which are less transferable, and if such is the case no images are obtained. Adequate adhesives are for example: for use in the transfer liquid: gum arabic in water, polyvinyl alcohol in water or in a mixture of water and alcohol; dextrin and fish glue in water; for application on receiving supports: gelatin, polyvinyl alcohol, casein, various artificial resin emulsions.

If the remnant image is to be used for contact printing by light transmission, then naturally the quality of that image should be brought up to the highest pitch of excellence, i.e. the transfer should be as complete as possible. The examples will describe screen sheets, which upon transfer on suitable receiving supports will yield good remnant images. it goes Wlil'lOLli saying, that the light-sensitive screen sheets according to the invention may also be used without going through the process of screen reflectography proper. One can form an image, by projection (in the making of an enlargement from a microfilm representing printed matter) or by contact printing by light transmission, upon the lightsensitive screen sheets upon that side upon which, in the making of the screen reflex copy, the light reflected by the original would fall. Also an imagewise exposure can be effected from the other side, provided the light-sensitive screen sheet be in contact with a diffusely reflecting background. After such exposure one of the transfer processes described above is used for making a transfer image and/or a useful remnant image. These transfer images and remnant images can each have their particular advantages. These advantages will depend inter alia on the pigment used in the screen parts.

By far the greater number of the examples are based on the use of one and the same diazo compound. This is the condensation product of p.-diazo-diphenylarnine and formaldehyde prepared according to Example I of Netherlands Patent No. 35,480.

This diazo compound is referred to in the examples as diazo aldehyde for the sake of brevity. The examples serve the purpose of illustrating the various embodiments of process and screen sheets according to the invention and by using the same diazo compound, the respective results of the examples are comparable with one another. Apart from this some examples utilizing other compositions of the light-sensitive material are given.

Likewise for the sake of brevity the terms cellulose acetate sheet and gelatin' are used Without further indication. By cellulose acetate sheet is to be understood a sheet having an acetyl content corresponding to 50% by weight of combined acetic acid; the sheet if not otherwise indicated having a weight of 80 g./m. By "gelatin without further indication there is to be understood the type Super Photo 10-5. This acetate sheet and this gelatin are merely examples of numerous suitable qualities. The examples only use one quality in order to make the results better comparable with one another.

The same considerations apply to carbon black and asphalt." By way of example carbon black of the type Kosmos-20 has always been used; the asphalt used is always of the type Ennjay Oxydized Asphalt 285/300 M.P.

The same considerations apply to the term transparent paper; for the reason mentioned, transparent paper No. 5-1582, Super transparent of 90 g./rn. was always used.

Likewise for the sake of brevity and for better comparison the examples only mention deacylating of cellulose acetate sheets without further description. This deacylation was carried out as follows:

The cellulose acetate sheet was dipped for 1 sec. and at a temperature of 28 C. in a solution consisting of:

600 cm. ethyl alcohol 50 cm. water 43 g. potassium hydroxide Thereafter the sheet was dried so that it had become dry exactly after 20 seconds. It was then again dipped for 1 /2. second at a temperature of 27 C. in the following liquid:

600 crn. ethyl alcohol 300 cm. water 72 g. potassium hydroxide 2t) and it was then dried so as to be dry after exactly 10 seconds. It was thereafter washed in running water for 30 seconds and immediately thereafter dipped for 7.5 seconds at room temperature in a solution of the following composition:

600 cm. ethyl alcohol 3150 cm. water g. oxalic acid Thereafter the sheet was so dried that it became dry after exactly 12 seconds.

This is one of the many suitable methods of deacylating and it is referred to in the following examples as deacylating. The use of one single type of the materials mentioned and the application of one single method of deacylating in the examples should not be understood in any respect whatsoever as a limitation. This, as will be clear, also applies to the method of pressing together the exposed light-sensitive sheet and the receiving support, for which manipulation all the examples make use of the apparatus according to FIGURE 16 or 17.

Example I On one side of a cellulose acetate sheet there is formed by casting at 40 C. with a solution of:

120 g. gum arabic 52 g. gelatin 12 g. diazoaldehyde 1000 cm. water and drying, a light'sensitive layer of approximately 3 g/m. This layer is then moistened by means of a solution of:

12 g. diazoaldehyde 500 cm. ethyl alcohol 500 cm. water and thus made adhesive, without its diazoaldehyde content being appreciably changed. By means of a rubber roller the sheet is pressed with its adhesive side against a cylinder, the surface of which consists of a layer of deacylated cellulose acetate and which has the form of an intaglio screen relief. This surface was obtained as follows:

A cellulose acetate sheet of 500 g./m. was superficially moistened with acetone and pressed against a hardened gelatin screen relief. After removal of the gelatin relief, the cellulose acetate sheet had, at its surface, taken an intaglio screen relief of the usual form, which had a linear period of microns, whilst the depth of the screen cupules, on the average, was 12 microns. The joint surface of the screen cupules covers approximately of the total surface area. Thereafter the cellulose acetate sheet was deacylated. This deacylated sheet was mounted around a metal cylinder with its screen side outwards. Before pressing the above described lightsensitive sheet with its adhesive surface against the screen cylinder, its intaglio screen relief had been filled with a pigment suspension of the following composition:

200 g. carbon black 40 g. asphalt 1000 cm. xylene whereafter it was dried. The elevations of the relief were cleaned by means of a rotating flannel disc, so as to leave the dry black pigment mass (hydrophobic screen parts, porous to Water, but impervious to light) only in the screen cupules and no longer on the elevations. The light-sensitive sheet now takes, by means of its adhesive light-sensitive layer, the screen parts out of the intaglio screen relief. In the light-sensitive screen sheet thus formed the screen parts (1 in FIGURE 1 and in FIG- URE 6) have the form of islands. The light-sensitive material 2, underlaying the screen parts, is water reccptive and swellable and can take up water right through the porous screen parts.

The light-sensitive screen sheet thus formed, is brought into uniform contact with a page printed matter in the apparatus according to FIGURE 15; (the situation then is that of FIGURE 1; and upon the exposure as indicated by the reference numbers 10, 27 and 29 in FIGURE 15). The exposure takes 120 seconds. (This is one of the many suitable methods for exposing and it is, in the following examples, referred to as exposure, and in these examples, if not otherwise indicated, it always is supposed that the exposure takes place in the manner of the screen reflectography.)

In the transfer step which follows, a sheet transparent paper, carrying on one side a gelatin layer of approximately 3 g./rn. serves as the receiving support.

For carrying out the transfer the receiving support and the exposed screen sheet are both dipped for 1 second in water of room temperature and thereafter they are passed, transfer surfaces against each other, through the apparatus of FIGURE 16 at a speed of 2 mimin. and at a transfer pressure of 2 kg. per running cm. Immediately thereafter the sheets are separated from each other. The transfer is almost complete and thus nearly corresponds with the conception of FIGURE 10. The trans fer image is a transparent positive and the remnant image a transparent negative. From the first, positive copies can be produced on diazotype paper and from the second, positive copies can be produced on negative photographic materials and on blueprint paper.

When not otherwise indicated, the transfer, in the following examples, will, as above, be carried out at room temperature.

When those portions of the light-sensitive layer, which, upon exposure, were located between the screen parts 1 and the dark-portions 5 of the original 4 (FIGURE 1), are called A-portions and the others the B-portions, then the course of things perhaps can best be summed up as follows:

The A-portions kept their original properties and, up on the transfer, they have taken up water right through the porous screen parts, and have swelled up. As a consequence thereof the A-portions have permitted the transfer of those screen parts which were linked to them. In the B-portions the properties have been altered to the extent that the screen parts which were linked up with them could not be repelled; on the contrary these screen parts have, as it were, been fastened. With the B-portions one could say that their receptivity for water and their capacity of swelling have been decreased and that their power to adhere has been increased.

Example II A cylinder with a screen relief of deacylated cellulose acetate, according to Example I, is used, but the screen relief now has the form of crossed canals, encircling islands. The linear period is 85 microns, the depth of the canals -14 microns and the joint surface of the elevated screen portions (islands) covers approximately 10% 0f the total surface area.

In this screen relief dry screen parts are formed in the manner of Example I, but the pigment suspension used, is of the following composition:

250 g. carbon black 50 g. asphalt 1000 cm. xylene Upon this screen relief on the cylinder, thus filled with hydrophobic and to water porous screen parts, a lightsensitive layer is applied consisting of:

400 cm. of a solution of 30% by weight of gum arabic in water 250 cm. of a solution of by weight of gelatin in water 350 cm. water 10 g. diazoaldehyde 22 The light-sensitive layer formed, after drying will have a weight of 3.54 g./rn. This layer is moistened at 20 C. with the following solution:

500 cm. ethyl alcohol 500 cm. water 10 g. diazoaldehyde by which treatment its surface will become adhesive.

By means of a rubber roller, a dry web of deacylated cellulose acetate is now pressed, in the manner of Exampie I, against the cylinder, carrying the screen parts, and the light-sensitive layer. The light-scnsitive layer, overlaying the screen parts on the cylinder, will adhere to the support and when the support is taken away from the cylinder, the light-sensitive layer and the screen parts (in the screen relief) will have transferred from the cylinder onto the support.

The light-sensitive material 2 now, according to FIG- URE 1, being located between screen parts 1 and sup port 3, is water receptive and swellable and it can, right through the porous screen parts 1, take up water.

Thus there results a light-sensitive screen sheet, the light-pervious portions of which (located between the screen parts) have the form of islands, like the light-pervious portions 8 in FIGURE 7.

The light-sensitive screen sheet is submitted to an exposure of 240 seconds. The transparent paper with gelatin layer of Example 1 serves as the receiving support.

The transfer is carried out as follows: receiving support and exposed screen sheet are both immersed for 5-10 seconds in water, to which 0.1% of Ilford wetting agent has been added, and thereafter the two sheets together are passed through the apparatus of FIGURE 16 at a speed of 3 m. and at a transfer pressure of 2 kg. The sheets are separated; the transfer image is a transparent positive; the remnant image a transparent negative. Both can be recopied.

Example III Dry screen parts are formed in a cylinder with a relief surface as described in Example II, the suspension, for the formation of the screen parts in that relief, however being the following:

46 g. diazoaldehyde 210 g. gum arabic 70 g. carbon black 56 cm. gelatin 980 cm. Water 63 cm. ethyl alcohol 1.5 g. glycerol The screen parts are hydrophilic. Against the screen surface of the cylinder, filled with screen parts, a web of transparent paper is pressed, which web carries on one side a gelatin layer of approximately 2.5 g./m. which gelatin layer had immediately previous to the pressing, been moistened with a mixture of:

400 cm. water 600 cm? ethyl alcohol 10 g. diazoaldehyde The web will take the screen parts over from the cylinder surface. After separation the screen sheet formed, will thus carry screen parts, which contain in their mass lightsensitive material.

The light-pervious screen portions located between these screen parts, have the form of the islands 8 in FIG- URE 7.

Exposure: 330 seconds, with the screen parts in contact with the printed matter. A sheet of white paper with a well calendered smooth surface serves as receiving support.

The transfer is carried out as follows: Receiving support and exposed screen sheet are both immersed for 5-10 sec. in water, to which 0.1% of Ilford wetting agent has been added. Thereafter they are passed through the ap- 23 paratus of FIGURE 16 at a speed of 2.5 m. and at a transfer pressure of 2.25 kg. The sheets are separated; the transfer image is positive; the remnant image a transparent negative.

It may be assumed that in this transfer the important factors are: the decrease of the water receptivity of the screen parts which upon exposure were in contact with the clear parts of the original, and the adhesive power of the screen parts, which upon exposure were located above the dark parts of the original. The transfer is not complete (compare FIGURE 9) and the remnant image in consequence is of less good quality. A second transfer can be carried out and thereby the remnant image will become stronger.

Example IV The cylinder with a screen relief as described in ExampleI is used. The screen cupules are filled with dry screen parts obtained by means of the following pigment suspension:

200 g. carbon black 32 g. asphalt 1000 cm. xylene 400 cm. of a solution of 3% by weight of cellulose acetate butyrate of the type AB 500/ I (this is one of the many suitable binding agents for the pigment matter and it will be referred to in the following examples as cellulose acetate butyrate") 48 cm. propylene glycol The screen parts are porous to water and slightly hydrophobic. Transparent paper, provided at one side with gum arabic, is moistened by means of a mixture of equal volumes of ethyl alcohol and water at 20 C. at its gummed side, and with this gummed side is pressed against the cylinder. After leaving the cylinder it will have taken the screen parts from said cylinder. The screen side of the transparent paper is, by casting and drying, provided with a gelatin layer of 2.5-3 g./m. and this layer is superficially impregnated with a solution of 22 g. diazoaldehyde 80 cm. ethyl alcohol 20 cm. water and thereafter again dried. The light-sensitive screen sheet obtained, it assembled according to FIGURE Exposure: 30 seconds.

For illustration, reference is made to FIGURE 2, in which 3, 1 and 2 correspond with 3, 1 and 2 of FIGURE 4. Furthermore with FIGURE 15 in which the light-sensitive screen sheet is indicated by 10 and the original by 29.

Upon exposure those portions of the light-sensitive material 2 of FIGURE 2, located between the screen parts 1 and the dark portions 5 of the original 4 undergo no, or at any rate little, alternation and essentially keep their properties; receptivity for water and swelling power and adhesive power upon moistening with water. In all other portions these properties are decreased.

White writing paper, white coated paper or white bond paper serve as receiving support.

The transfer is carried out as follows: The screen sheet is immersed in water for seconds and then, together with the receiving support, passed through the apparatus of FIGURE 16 at a speed of 2.5 m. and at a transfer pressure of 2 kg. The sheets separated; the transfer image is positive; the remnant image an imperfect negative. The remnant image, in consequence of the imperfections of the transparent paper, has it is true, no perfectly clear transparent portions (it consequently is more or less as illustrated in FIGURE 9), but nevertheless one can. in transmitted light, make a reasonably good copy from it on lightsensitive material such as diazotype paper.

Instead of natural tracing paper one may also start with a web of cellophand of 80 g./m. and this may be processed in the same manner and may yield similar results, which, in as much as the transparent portions of the remnant image are concerned, are better.

Example V A light-sensitive screen sheet according to FIGURE 4 is formed in the manner of Example IV, but now, as a support for the screen sheet, a deacylated sheet of cellulose acetate is used.

Exposure and transfer are carried out in the manner of Example IV. Similar results are obtained.

The remnant image is of good quality (FIGURE 10); it may be used for recopying on blueprint paper by the ordinary contact-printing process with transmitted light.

Example VI In one side of a cellulose acetate sheet a relief is pressed as illustrated in FIGURES 7 and 14, with a screen pattern according to FIGURE 7. The elevations 8 are located in rectilinear rows, which are perpendicular to each other and their mutual center distance 9 measured horizontally or vertically according to FIGURE 5 (in the following examples for convenience called center distance 9) is microns, whilst the diameter of the upper-surface of the elevations 8 in FIGURE 7 (21 in FIGURE 14) is 32 microns. The elevations have somewhat the form of cones so that the diameter at their base is somewhat greater than 32 microns. The elevations 21 lay approximately 10 microns higher than the average level of the depths 2t), encircling them. The relief is cast with the following suspension:

33 g. diazoaldehyde 300 gum arabic g. carbon black 1000 cm. water 90 cm. ethyl alcohol 2 cm. glycerol so that the depths 20 of the relief are filled up.

After drying, the tops 21 are cleaned by means of soft smooth leather. Thus, on the sheet, a screen is formed with light-pervious islands 8 (FIGURE 7), between the screen parts 1. The center distance 9 is, as already said above, 90 microns, whilst the light-pervious screen portions 8 (FIG. 7) (21 in FIGURE 14) cover 10% of the total surface area (the percentage ratio of the surface area of the light-pervious screen portions to the total surface area will for the sake of brevity be called in the following examples the light transmittance). The screen parts 1 (FIG. 14) thus formed are porous to water and, at their accessible side, adhesive upon moistening. Exposure: 80 seconds. White, coated paper or Writing paper serves as receiving support.

The transfer is carried out as follows: the exposed screen sheet is immersed in Water for some seconds and thereafter, together with the receiving support, passed through the apparatus of FIGURE 16 at a speed of 2 m. and at a transfer pressure of 2 kg. The sheets are separated; the transfer image is positive. The transfer however is very incomplete, so that the remnant image is practically invisible.

Instead of the support of cellulose acetate one may, for the light-sensitive screen sheet, use other transparent sheets in which a relief, as described above, can be formed, e.g. sheets of polyvinyl acetate, polyvinylacetate with a low acetyl content, Celluloid, etc.

Example VII At a temperature of l820 C. there is cast on one side of a cellulose acetate sheet a solution of 20 g. gum arabic 1 g. diazoaldehyde 1G0 cm water After drying, a light-sensitive layer of 9-10 g./m. is thus 25 formed. This layer is moistened with the following solution:

1.25 g. diazoaldehyde 30 cm. ethyl alcohol 30 cm. water By this treatment the layer will become mouldable, without the diazoaldehyde content being decreased.

Thereafter a screen relief is impressed as in Example VI. This relief consists of the elevations 21 (FIG. 13) and the depths 29. The center distance 9=80 microns; the light transmittance=25%. After drying, screen parts 1 are formed in the relief (as in Example VI) by means of a pigment suspension consisting of:

200 g. carbon black 24 g. asphalt 1000 cm. xylene The hydrophobic, porous, screen parts 1 will reasonably well be linked up with the bottoms 20 of the screen cavities in the light-sensitive gum layer 2, but by the application of some pressure and with the use of water at room temperature, they can be transferred onto the receiving support.

The porosity of the screen parts 1 will, upon transfer, have a favourable influence thereon.

Exposure: 150 seconds.

Transparent paper with a gelatin layer of 4 g./m. serves as receiving support.

The transfer is carried out as follows: The screen sheet is immersed in water during 5 seconds and thereafter, together with the receiving support (gelatin side turned towards screen sheet), passed through the apparatus of FIG. 16 at a speed of 4 m. and at a transferpressure of 2 kg. The sheets are separated. The transfer image is a transparent positive and after drying is highly resistant to finger-marking, the remnant image being a transparent negative. Both can be recopied.

Example VIII In one side of a cellulose acetate sheet a relief is impressed as described in Example VI. Center distance 9":80 microns; light transmittance=18.5%.

Thereafter at a temperature of 40 0, there is cast on the relief side an emulsion consisting of 8 g. gelatin 1 g. diazoaldehyde 100 cm? water After drying, the light-sensitive layer 2, thus formed, weighs 2-2.5 gJmP. The relief remains almost entirely intact because the layer formed has only little thickness (FIG. 12).

The screen parts 1 are formed in the manner of Example VI from a pigment suspension of the following composition:

240 g. carbon black 96 g. asphalt 1000 cm. xylene The support 3 is hydrophilic, at any rate at its surface. The screen parts 1 are hydrophobic and porous to water; they are relatively strongly linked up with the bottoms of the cavities 20, and to the light-sensitive material 2 located thereon; their linkage with the sheet 3 is nevertheless moderated to the extent that, upon transfer onto moistened gelatinized paper, they are transferred. Upon the transfer-operation the light-sensitive layer 2 takes up moisture (inter alia right through the porous screen parts 1) and this promotes the transfer.

Exposure: '120 seconds.

Transparent paper provided with a gelatin layer of 3 4 g./m. serves as receiving support.

The transfer is carried out as follows: The exposed screen sheet is immersed for seconds in a mixture of equal volumes of ethyl alcohol and water and thereafter 26 is, together with the receiving support (gelatin side against screen side of screen sheet), passed through the apparatus of FIGURE 16 at a speed of 2.5 m. and at a transfer pressure of 1.75 kg. The sheets are separated; the transfer image is a transparent positive; the remnant im age a transparent negative. Both can be recopied.

Example IX In one side of a cellulose acetate sheet a relief is impressed, as described in Example VI. Center distance 9=90 microns; light transmittance=10%. The sheet is deacylated; the relief remains intact. The elevations are like 21 in FIG. 12; the screen cavities like 20. The screen side of the sheet is impregnated with the following solution:

4 g. diazaldehyde 50 cm. ethyl alcohol 50 cm. water The solution is doctored olf by means of a soft rubber roller. Thereafter the sheet is dried. A light-sensitive zone has thus been formed in the deacylated relief surface. This is as schematically indicated in FIG. 12 by means of the dotted line 2 (which function corresponds to the dotted line 2 in FIG. 1). The screen parts 1 are formed in the manner of Example VI from a pigment suspension of the following composition:

200 g. carbon black 50 g. asphalt 1000 cm. Xylene The support 3 is hydrophilic, at any rate at its surface. The screen parts 1 are hydrophobic and porous to water; they are rather strongly linked up with the bottoms 20 of the cavities, and to the light-sensitive material 2 located thereon. Their linkage with sheet 3 is nevertheless moderated to the extent that upon transfer onto moistened, gelatinized paper they are transferred.

Upon the transfer-operation the light-sensitive layer 2 takes up moisture (inter alia right through the porous screen parts 1) this promoting the transfer.

Exposure: 150 seconds.

Transparent paper with a gelatin layer of 34 g./m.= serves as receiving support.

The transfer is carried out as follows: Both the screen sheet and the receiving support are immersed in water for 5 seconds and thereafter (gelatin side turned towards screen sheet) passed through the apparatus of FIG. 16 at a speed of 3 m. and at a transfer pressure of 1.8 kg. The sheets are separated. The transfer image is a transparent positive, the remnant image a transparent negative. Both can be recopied.

Upon transfer the results were as follows: Only those portions in which the light-sensitive layer 2 remained unexposed took up water in a sufficient quantity, and these portions more easily release the screen parts 1 (than do the exposed portions) so that these screen parts were taken over by the receiving support.

Example X In one side of a cellulose acetate sheet a relief is impressed as described in Example VI.

Upon the relief side there is cast, at a temperature of 30 C., the following solution: 20 g. dextrin 1 g. diazoaldehyde cm. water After drying, the light-sensitive layer 2 thus formed will weigh approximately 4 g./m. The relief remains intact, at any rate to a considerable extent. The screen parts 1 are formed in the manner of Example VI, from a pigment suspension of the following composition: 240 g. carbon black 48 g. asphalt 1000 cm. xylene The screen parts 1 are hydrophobic and porous to water; they are rather strongly linked up with the bottoms 20 of the cavities and to the light-sensitive material 2 located thereon. Their linkage with sheet 3 is nevertheless moderated to the extent that upon transfer onto moistened gelatinized paper they are transferred. Upon the transferoperation the light-sensitive layer 2 takes up moisture (inter alia right through the porous screen parts 1) this promoting the transfer.

Exposure: 240 seconds.

Transparent paper with a gelatin layer of 3-4 g/m. serves as receiving support.

The transfer is carried out as follows:

The receiving support is immersed for -10 seconds in a mixture of equal volumes of ethyl alcohol and water and thereafter, together with the exposed screen sheet (gelatin side of receiving support against screen side of the screen sheet) is passed through the apparatus of FIG. 16 at a speed of 3 m. and at a transfer pressure of 1.8 kg. The sheets are separated; the transfer image is a transparent negative; the remnant image transparent positive. Both can be recopied.

In each of the following examples a light-sensitive screen sheet is manufactured according to the principle of FIGS. 2 and 4 but an assembly according to FIG. 11 and then processed.

For the sake of simplicity in all these examples the support 3 always is a cellulose acetate sheet. This support, however, may equally well consist of another lightpervious material, such, for example, as transparent paper, cellophane, Celluloid or even glass, which is provided on one or both sides with a layer of cellulose acetate. Instead of cellulose acetate (which, as Will be indicated, is generally deacylated) naturally other material may be used, like polyvinylacetate, which may be deacylated or not. In all the cases the surface is made mouldable, for example by heating or moistening (for example with acetone).

Into this mouldable surface a screen relief with elevations 21, surrounded by cavities 20, is impressed. The height of the elevations 21 over the average level of the bottoms of the cavities 20 is in all examples approximately microns. This height could also be smaller or greater than 10 microns but in practice heights of smaller than 5 microns and greater than microns are less desirable. The screen pattern in all examples is that of FIG. 7, wherein 8 represents the elevations and 1 the cavities. The relief surface is, when not otherwise indicated, deacylated. After the deacylation the screen relief remains practically unaltered as compared to its condition before the operation.

The screen parts 1 (FIG. 11) are formed in the cavities by means of a finely ground pigment suspension. After drying this pigment suspension, the elevations 21 are cleaned by means of soft smooth leather. In the screen pattern thus formed the light-pervious screen portionslike 8 in FIG.7have the form of islands.

After the formation of the screen sheet, the lightsensitive material 2 (FIG. 11), generally a layer of a lightsensitive material which contains a lyophilic binding agent, is deposited on the screen side.

The production of the reflex copy is (for the sake of simplicity) as in the previous examples, in an apparatus according to FIG. 15, and the light-sensitive screen sheet, and the original to be copied, are positioned in contact with each other as diagrammatically shown in FIG. 2. In this arrangement, in consequence, the light-sensitive screen sheet consists of 3, 1 and 2, whilst the original 4 carries the dark areas 5. The light is incident according to arrow 6.

In FIG. 15 the light from lamp 22 follows the arrows 26 through the glass cylinder 24 and passes through the light-sensitive screen sheet 10 underneath which the original 29 to be copied (with its dark areas 27) is located.

The transfer is carried out as indicated in each example with or without transfer-liquid. For the operation of pressing-together, when not otherwise indicated, the apparatus according to FIG. 16 is used.

Example XI One side of a cellulose acetate sheet is impressed, with a center distance 9"=l00 microns; and a light transmittance"=7.8%. The sheet is deacylated.

The pigment suspension for the forming of the screen parts has the following composition:

240 g. carbon black 24 g. asphalt 1000 cm. xylene 1000 cm. of a solution of 10% by weight of cellulose acetate butyrate in ethyl acetate The screen parts are hydrophobic and not porous.

The light-sensitive layer is formed by casting with the following solution:

60 g. gelatin 10 g. diazo-aldehyde 1000 cm. water and drying. The layer weighs 3 g./m. It is receptive for water, swellable with water, and becomes adhesive upon moistening with water. It makes thorough contact with the deacylated tops of the relief.

Exposure: 150 seconds.

White, coated paper serves as receiving support.

The transfer is carried out as follows: The screen sheet is immersed in water for 35 seconds and thereafter pressed together with the receiving support at a speed of 2.5 m. and at a transfer pressure of 3.5 kg.

The sheets are separated. The transfer image is a positive, and after drying is highly resistant to fingermarking and sprinkling with water; the remnant image is a transparent negative.

Example XII In one side of a cellulose acetate sheet a screen relief is impressed. Center distance 9=80 microns; light transmittance:l0%. The sheet is deacylated.

The pigment suspension for the forming of the screen parts has the following composition:

200 g. carbon black 32 g. asphalt 400 cm. of a solution of 3% by weight of cellulose acetate butyrate in ethyl acetate 48 cm. propylene glycol 1000 cm. xylene The screen parts are porous to water and slightly hydrophobic. The lightsensitive layer is formed by casting with the following solution:

9 g. gelatin 0.5 g. diazoaldehydc cm. water and drying. The layer weighs appr. 2 g./m. it is receptive for water, swellable with water and becomes adhesive upon moistening with water. It makes thorough contact with the deacylated tops of the relief. One can also first form the gelatin layer and subsequently sensitize it with diazoaldehyde solution.

Exposure: 40 seconds.

White, coated paper serves as receiving support.

The transfer is carried out as follows: The exposed screen sheet is immersed in water for a few seconds and thereafter pressed together with the receiving support at a speed of 2 m. and at a transfer pressure of 3 kg.

The sheets are separated. The transfer image is positive, the remnant image being a transparent negative.

Reversed results may be obtained if the transfer temperature is chosen between 35 and 60 C. Then there will be formed, upon transfer, on white, coated paper a non-reversed negative image. A transparent positive remnant image remains in the screen sheet from which positive copies can be produced, c.g. on diazotype paper.

Example XIII In one side of a cellulose acetate sheet a screen relief is impressed. Center distance 9=80 microns; light transmittance=l%. The sheet is deacylated.

The pigment suspension for forming the screen parts has the following composition:

200 g. carbon black 50 g. asphalt 1000 cm. xylene The screen parts are hydrophobic and porous to water; they have only little linkage with the hydrophilic bottoms of the relief. The light-sensitive layer is formed by casting with the following solution:

9 g. gelatin 100 cm. water and after drying it is sensitized by means of the following solution:

1 g. ammonium bichromate 20 cm. water 80 cm. ethyl alcohol and dried again. The layer weights 2 g./m. it is receptive for water, swellable with water and becomes adhesive upon moistening with Water.

Exposure: 100 seconds.

White, coated paper serves as receiving support.

The transfer is carried out as follows: The exposed screen sheet is immersed in water for 2 seconds and thereafter pressed together with the receiving support at a speed of 2.5 m. and at a transfer-pressure of 3 kg.

The sheets are separated. The transfer image is positive; the remnant image is a transparent negative.

Example XIV In one side of a cellulose acetate sheet a screen relief is impressed. Center distance 9"=80 microns; light transmittance=10%. The sheet is deacylated.

The pigment suspension for forming the screen parts has the following composition:

200 g. carbon black 32 g. asphalt 400 cm} of a solution of 3% by weight of cellulose-acetate butyrate in ethyl acetate 48 cm. propylene glycol 1000 cm; xylene The screen parts are but slightly hydrophobic and porous to water; they have only little linkage with the bottoms of the relief. The light-sensitive layer is formed by casting with the following solution:

9 g. gelatin 1 g. sodium salt of 4.4'-diazidostil-bene-2.2-disulphonic acid 1000 cm. water and drying. The layer weighs 2-2.5 g./m. it is receptive for water, swellable with water and becomes adhesive upon moistening with water. It makes thorough contact with the dcacylated tops of the relief.

Exposure: 80 seconds.

White, coated paper serves as receiving support.

The transfer is carried out as follows: The exposed screen sheet is immersed in water of l0-20 C., preferably 18 C., for 12 seconds and thereafter pressed together with the receiving support at a speed of 2.5 In. and at a transfer pressure of 3 kg.

The sheets are separated. The transfer image is positive, the remnant image being a transparent negative.

Example XV In one side of a cellulose acetate sheet a screen relief is impressed. Center distance 9=80 rnicnons; light transmittance =25%. The sheet is deacylated.

The pigment suspension for forming the screen parts has the following composition:

13.5 g. carbon black 1.33 g. cellulose acetate butyrate cm. ethyl acetate The screen parts are hydrophobic and porous to water; they have only little linkage with the bottoms of the relief. The light-sensitive layer is formed by casting with the following solution:

8 g. gelatin 100 cm. water and after drying, sensitizing with a solution of:

4 g. of the borofiuoride of p.diazoaniline in 100 cm. water and dried again. The layer weighs 2 g./m. it is receptive for water, swellable with water and becomes adhesive upon moistening with water.

Exposure: 360 seconds.

White, smooth writing paper serves as receiving support.

The transfer is carried out as follows: In an apparatus according to FIG. 17 the gutter 48 is filled with distilled water and the apparatus is put in motion. The sheet indicated at 43 is the exposed screen sheet with its screen side downwards and sheet 46 is the receiving support. The apparatus is operated at a speed of 3 m. and at a transfer-pressure of appr. 1 kg. The quantity of water which roller 45 supplies to sheet 43 is appr. 20 g./m.

The sheets are separated. The transfer image is positive, the remnant image being a transparent negative.

Example XVI In one side of a cellulose acetate sheet a screen relief is impressed. Center distance 9=80 microns; light transmittance=25%. The sheet is deacylated.

The pigment suspension for forming the screen parts has the following composition:

13.5 g. carbon black 1.33 g. cellulose acetate butyrate 100 cm. ethyl acetate The screen parts are hydrophobic and porous to water; they have only little linkage with the bottoms of the relief. The light-sensitive layer is formed by casting with the following solution:

8 g. gelatin in 100 cm. water and after drying, sensitizing with a solution of:

4 g. p.diazo-ethyl-beta-hydroxyethylaniline in 100 cm. water and dried again. The layer weighs 2 g./m. it is receptive for water, swellable with water and becomes adhesive upon moistening with water.

Exposure: 360 seconds.

White, smooth writing paper serves as receiving support.

The transfer is carried out as follows: In an apparatus according to FIG. 17 the gutter 48 is filled with distilled water and the apparatus is put in motion. The sheet indicated at 43 is the exposed screen sheet with its screen side downwards and sheet 46 is the receiving support. The apparatus is operated at a speed of 3 m. and at a transfer-pressure of appr. 1 kg. The quantity of water which roller 45 supplies to sheet 43 is appr. 20 g./m.

The sheets are separated. The transfer image is positive; the remnant image being a transparent negati e.

Example XVII In one side of a cellulose acetate sheet a screen relief 31 is impressed. Center distance 9:80 microns; light transmittance=25%. The sheet is deacylated.

The pigment suspension for forming the screen parts has the following composition:

13.5 g. carbon black 1.33 g. cellulose acetate butyrate 100 crn. ethyl acetate The screen parts are hydrophobic and porous to water; they have only little linkage with the bottoms of the relief. The light-sensitive layer is formed by casting with the following solution:

8 g. gelatin in 100 cm. Water drying and sensitizing with a solution of:

4 g. p.diazo-ethyl-beta-diethylaminoethylaniline in 100 cm. water and dried again. The layer weighs appr. 2 g./m. it is receptive for water, swellable with Water and becomes adhesive upon moistening with water.

Exposure: 360 seconds.

White, smooth writing paper serves as receiving support. The transfer is carried out as follows: In an apparatus according to FIG. 17 the gutter 43 is filled with distilled water and the apparatus is put in motion. The sheet indicated at 43 is the exposed screen sheet with its screen side downwards and sheet 46 is the receiving support. The apparatus is operated at a speed of 3 m. and at a transfer pressure of appr. 1 kg. The quantity of water which roller 45 supplies to sheet 43 is appr. 20 g./m.

The sheets are separated. The transfer image is positive; the remnant image is a transparent negative.

Example XVIII In one side of a cellulose acetate sheet a screen relief is impressed. Center distance 9:80- microns; "light transmittance:25%. The sheet is deacylated.

The pigment suspension for the forming of the screen parts has the following composition:

13.5 g. carbon black 1.33 g. cellulose acetate butyrate 100 cm. ethyl acetate The screen parts are hydrophobic and porous to water; they have only little linkage with the bottoms of the relief. The light-sensitive layer is formed by casting with the following solution:

8 g. gelatin in 100 cm. Water drying and sensitizing with a solution of:

4 g. p.diazomonoethylaniline in 100 cm. Water and dried again. The layer weighs appr. 2 g./m. it is receptive for water, swellable with Water and becomes adhesive upon moistening with water.

Exposure: 360 seconds.

White, smooth writing paper serves as receiving support.

The transfer is carried out as follows: In an apparatus according to FIG. 17 the gutter 48 is filled with distilled water and the apparatus is put in motion. The sheet indicated at 43 is the exposed screen sheet with its screen side downwards and sheet 46 is the receiving support. The apparatus is operated at a speed of 3 m. and at a transfer-pressure of appr. 1 kg. The quantity of water which roller 45 supplies to sheet 43 is appr. 20 g./m.

The sheets are separated. The transfer image is positive; the remnant image is a transparent negative.

32 Example XIX In one side of a cellulose acetate sheet a screen relief is impressed. Center distance 9:80 microns; light transmittance:l0%. The sheet is deacylated.

The pigment suspension for the forming of the screen parts has the following composition:

260 g. carbon black 50 g. asphalt 1000 cm. xylene The screen parts are hydrophobic and porous to water; they have only little linkage with the bottoms of the relief. The light-sensitive layer is formed by casting with the following solution:

10 g. dextrin 1 g. diazoaldehyde cm. water and drying. The layer weighs appr. 2 g./m. and is soluble in water at room temperature.

Exposure: 100 seconds.

White, coated paper serves as receiving support.

The transfer is carried out as follows: The exposed screen sheet is immersed in a mixture of equal volumes of ethyl alcohol and water for 5 seconds and thereafter pressed together with the receiving support at a speed of 4 m. and at a transfer pressure of 2.5 kg.

The sheets are separated. The transfer image is negative, the remnant image being a transparent positive. As distinct from most of the examples, those screen parts were transferred which have linkage with the more exposed light-sensitive material. A possible explanation could be that the unexposed dextrin-diazoaldehyde matter easily and rapidly looses its linkage with the screen parts, at any rate partiallyin Water of room temperature--Whilst the exposed matter keeps sufficient linkage with the screen parts and at the same time will show sufficient attachment to the receiving support.

Example XX In one side of a cellulose acetate sheet a screen relief is impressed. Center distance 9:80 microns; light transmittance=l0%. The sheet is deacylated.

The pigment suspension for forming the screen parts has the following composition:

200 g. carbon black 50 g. asphalt 1000 cm. xylene The screen parts are hydrophobic and porous to water; they have only little linkage with the bottoms of the relief. The light-sensitive layer is formed by casting with the following solution:

crn. Le Page fish glue 10 g. diazoaldehyde 875 cm. water and drying. The layer weighs 22.5 g./m. and is soluble in water. It makes thorough contact with the deacylated tops of the relief.

Exposure: 90 seconds.

White, coated paper serves as receiving support.

The transfer is carried out as follows: Both the exposed screen sheet and the receiving support are immersed in water for 5 seconds and thereafter pressed together at a speed of 3.5 m. and at a transfer-pressure of 2 kg.

The sheets are separated. The transfer image is negative, the remnant image being a transparent positive which can be recopied on .diazotype paper.

Example XXI In one side of a cellulose acetate sheet a screen relief is impressed. Center distance 9=80 microns; light transmittance:l0%. The sheet is deacylated.

The pigment suspension for the forming of the screen parts has the following composition:

200 g. carbon black 32 g. asphalt 400 cm. of a solution of 3% by weight of cellulose acetate butyrate in ethyl acetate 48 cm. propylene glycol 1000 cm. xylene The screen parts are but slightly hydrophobic and porous to water; they have only little linkage with the bottoms of the relief. The light-sensitive layer is formed by casting with the following solution:

7.5 g. of an incompletely deacylated polyvinylacetate of the type Elvanol grade 31-31, 76-79% deacylated 1 g. diazoaldehyde 25 cm. ethyl alcohol 75 cm. water and drying. The layer weighs 2-2.5 gjmfi, it is receptive for water, and becomes adhesive upon moistening with water. It makes thorough contact with the deacylated tops of the relief.

Exposure: 100 seconds.

White, coated paper or writing paper serves as receiving support.

The transfer is carried out as follows: The receiving support is immersed in water for a few seconds and thereafter pressed together with the screen sheet at a speed of 2 m. and at a transfer-pressure of 2.5 kg.

The sheets are separated. The transfer image is positive, the remnant image being a transparent negative,

Example XXII In one side of a cellulose acetate sheet a screen relief is impressed. Center distance 9=8O microns; light transmittance"=l%. The sheet is deacylated.

The pigment suspension for forming the screen parts has the following composition:

200 g. carbon black 50 g. asphalt 1000 cm. xylene The screen parts are hydrophobic and porous to water; they have only little linkage with the bottoms of the relief. The light-sensitive layer is formed by casting with the following solution:

g. blood albumin i g. diazoaldehyde 100 cm. water and drying. The layer weighs appr. 2 g./m. it is receptive for water, swellable with water and becomes adhesive upon moistening with water. It makes thorough contact with the deacylated tops of the relief.

Exposure: 90 seconds.

White, coated paper serves as receiving support.

The transfer is carried out as follows: The exposed screen sheet is immersed in a mixture of equal volumes of ethyl alcohol and water for 1-2 seconds and thereafter pressed together with the receiving support at a speed of 4 m. and at a transfer-pressure of 3 kg.

The sheets are separated. The transfer image is positive, the remnant image being a transparent negative.

Example XXIII In one side of a cellulose acetate sheet a screen relief is impressed. Center distance 9=80 microns; light transmittance"=10%. The sheet is deacylated.

The pigment suspension for forming the screen parts has the following composition:

200 g. carbon black 50 g. asphalt 1000 cm. xylene 34 The screen parts are hydrophobic and porous to water; they have only little linkage with the bottoms of the relief. The light-sensitive layer is formed by casting with the following slightly ammoniacal solution:

12 g. casein 100 cm. water drying, and sensitizing with the following solution:

2 g. diazoaldehyde cm. ethylalcohol 20 cm. water and dried again.

The layer weighs appr. 2 g./m. it is receptive for water, swellable with water and becomes adhesive upon moistening with water. It makes thorough contact with the deacylated tops of the relief.

Exposure: seconds.

White, coated paper or ordinary writing paper serves as receiving support.

The transfer is carried out as follows: In an apparatus according to FIG. 17 the gutter 48 is filled with water and the apparatus is put in motion. The sheet indicated at 43 is the exposed screen sheet with its screen side downwards and sheet 46 is the receiving support. The apparatus is operated at a speed of 5 m. and at a transferpressure of 2 kg. The quantity of water which roller 45 supplies to sheet 43 is appr. 10 g./m.

The sheets are separated. The transfer image is positive, the remnant image being a transparent negative.

Example XXIV In one side of a cellulose acetate sheet a screen relief is impressed. Center distance 9=80 microns; light transmittance"=l0%. The sheet is deacyiated.

The pigment suspension for the forming of the screen parts has the following composition:

200 g. carbon black 50 g. asphalt 1000 cm. xylene The screen parts are hydrophobic. The light-sensitive layer is formed by casting with the following solution:

10 g. of a cellulose acetate of medium viscosity 1000 cm. acetone drying, and superficially sensitizing with the following solution:

2 g. diazoaldehyde 50 cm. acetone 50 cm. water and dried again. The layer weighs appr. 2 g./m.

Exposure: 60 seconds.

White, coated paper serves as receiving support.

The transfer is carried out as follows: The exposed screen sheet is immersed in acetone for 1-2 seconds and immediately thereafter pressed together with the receiving zupport at a speed of 3 m. and at a transfer-pressure of The sheets are separated. The transfer-image is positive and is highly resistant against sprinkling with water; the remnant image is a transparent negative.

Example XXV In one side of a cellulose acetate sheet a screen relief is impressed. Center distance 9":110 microns; light transmittance=l0%. The sheet is deacylated.

The pigment suspension for the forming of the screen parts has the following composition:

200 g. carbon black 50 g. asphalt 1000 cm. xylene The screen parts are hydrophobic and they have only 

1. A PHOTOGRAPHIC PROCESS FOR THE PRODUCTION OF A PIGMENT IMAGE ON A RECEIVING SURFACE, WHICH COMPRISES IMAGEWISE EXPOSING AT ACTINIC LIGHT A LIGHT SENSITIVE SHEET, SAID SHEET COMPRISING A SUPPORT CARRYING ADHERENTLY BUT TRANSFERABLY OVER ONLY ONE OF ITS SIDES A COMPOSITE STRUCTURE CONSISTING ESSENTIALLY OF A REFLECTOGRAPHIC LIGHT SCREEN AND PHOTOGRAPHICALLTY LIGHT-SENSITIVE MATERIAL LINKED TO THE LIGHT IMPERVIOUS PARTS OF SAID SCREEN, SAID MATERIAL BEING SUBSTANTIALLY FREE OF GRAINS THAT SCATTER SAID LIGHT AND COMPRISING A COLLOIDAL BINDER AND A COMPOUND WHICH UPON EXPOSURE TO SAID LIGHT MATERIALLY ALTERS AN ADHESION POWER OF SAID BINDER, SAID SCREEN BEING COMPOSED OF A MYRIAD OF LIGHT IMPERVIOUS SCREEN PARTS INTERSPERSED WITH SCREEN AREAS PERVIOUS TO SAID LIGHT, SAID SCREEN PARTS COMPRISING VISUALLY PERCEPTIBLE PIGMENT MATTER, AT LEAST PIGMENT MATTER CONTAINING PARTS OF SAID STRUCTURE BEING ADHERABLE TO SAID RECEIVING SURFACE WITH A STRENGTH GREATER THAN THAT OF THEIR ADHERENCE TO SAID SUPPORT, SO AS TO BE TRANSFERABLE BODILY FROM SAID SUPPORT TO SAID RECEIVING SURFACE, AND THE ADHERABILITY THEREOF TO SAID RECEIVING SURFACE BEING SUBSTANTIALLY CHANGEABLE IMAGEWISE BY IMAGEWISE EXPOSING SAID MATERIAL TO ACTINIC LIGHT SO THAT THE EXPOSURE FORMS IN THE EXPOSED AND THE RELATIVELY UNEXPOSED AREAS OF SAID STRUCTURE, RESPECTIVELY, DISTINCT GROUPS OF LATENT IMAGE PORTIONS PROCESSING AT LEAST AS TO PIGMENT MATTER CONTAINING PARTS THEREOF MATERIALLY DIFFERENT DEGREES OF ADHERABILITY TO SAID RECEIVING SURFACE; AFTER THE EXPOSURE PRESSING SAID RECEIVING SURFACE AGAINST THE IMAGE SIDE OF SAID SHEET AND RENDERING AT LEAST PIGMENT MATTER CONTAINING PARTS OF ONE ONLY OF SAID GROUPS MORE STRONGLY ADHERENT TO SAID RECEIVING SURFACE THAN TO THE OTHER PARTS OF SAID SHEET; AND THEREAFTER SEPARATING SAID RECEIVING SURFACE FROM SAID IMAGE SIDE AND THEREBY SELECTIVELY SEVERING AND TRANSRERRING FROM THE OTHER PARTS OF SAID SHEET AT LEAST PARTS OF SAID ONE GROUP OF LATENT IMAGE PORTIONS, INCLUDING PIGMENT MATTER OF SAID SCREEN PARTS CONTAINED IN SAID ONE GROUP, IN THE FORM OF A PIGMENT IMAGE OBTAINED IN ADHERENCE TO SAID RECEIVING SURFACE WITHOUT FURTHER DEVELOPMENT. 